CN101321227B - IP fax and its work method - Google Patents

Abstract

An IP fax and working method thereof, referring to the technical field of utilizing IP technique to fax. This invention includes a mail sending/receiving module, a session initialization protocol fax device, opposite user agents, further includes an IP fax server; a control order port of the mail sending/receiving module is connected with the IP fax server; after receiving by IP fax server, the IP fax server will send a feedback information to the mail sending/receiving module; the first input end of the IP fax server is connected with an input end of the session initialization protocol fax device so as to realize the inter-conversion flowing from T.38 to the fax file form; the second input end of the IP fax server is connected with an input end of the opposite user agents so as to realize the encapsulation to the session initialization protocol stack. The target of this invention is to provide a target of source file fax transmission which has distinct gradation, simple protocol, powerful function, supports multi-path fax session, fax file distributing mailbox and plural file forms.

Description

An IP fax device and its working method

technical field

The invention relates to the technical field of facsimile by using IP technology.

Background technique

At present, PBX (Private Branch Exchange) is widely used in enterprise offices, and plays an important role in improving the efficiency of enterprises. However, the traditional PBX adopts a special technology lacking openness and standardization, which is not only expensive, but also does not support the emerging CTI (Computer and Telephone Integration) and VOIP technology. In recent years, with the popularity of the Internet and the success of IP technology, IP-PBX based on IP protocol has emerged, which is expected to solve the shortcomings of traditional PBX.

The IP-PBX system realizes the integration of the functions of the computer network and the telephone exchange. Each telephone terminal in the IP-PBX network system adopts IP mode for data communication, which can not only make calls, but also realize the transmission of text, data and images, unify the telephone network and computer network as a whole, and realize electronic office in the local area network. Especially in long-distance collaborative business and electronic office, it will give full play to its powerful resource advantages and bring convenience to business cooperation and work reorganization.

The control center in the IP-PBX LAN can effectively manage the computer network and telephone network according to the specific situation, so as to achieve resource sharing. The IP-PBX networks in different regions can realize cheap long-distance communication, electronic office and e-commerce with the help of the Internet.

The research and development of the IP-PBX system has received many attentions, but at present the industry has only completed the development of finished products based on the H.323 protocol. However, the IP-PBX system that the author participates in developing is based on the SIP protocol (Session Initiation Protocol) and supports a variety of value-added services, which is still a new thing in the information field. Later development will also add functions such as instant message (Instant Message) and multimedia services that are currently widely used to this system. The final IP-PBX system will definitely be favored by many enterprise users and create huge economic benefits.

At present, most IP-PBX systems in the industry are developed based on the H.323 protocol standard.

Because the H.323 standard is too complex, it is too complicated or expensive for many products that only need basic "fast but not perfect" call control between network gateways. Moreover, H.323 cannot be integrated with SS7 (Signaling System #7, No. 7 signaling), or supplement the powerful functions that SS7 must provide.

Contents of the invention

The object of the present invention is to provide an IP fax with clear layers, simple protocol, powerful function, support for multi-channel fax sessions, fax file forwarding mailbox, source file fax sending in multiple file formats and its working method.

In order to achieve the above object, the present invention adopts the following technical solutions:

The invention includes a mail sending/receiving module, a session initiation protocol fax device, a back-to-back user agent, and an IP fax server. The control command port of the mail sending/receiving module is connected to the IP fax server, and the IP fax server will send feedback information after receiving to the mail sending/receiving module; the first output end of the IP fax server is connected to the input end of the session initiation protocol fax device, realizing the mutual conversion from the T.38 stream to the fax file format; the second output end of the IP fax server is connected to the back-to-back The input terminal connection of the user agent implements the encapsulation of the session initiation protocol stack;

The IP fax server includes a fax control module, a media processing module, and a call control module;

The fax control module includes a fax management module and a call state machine module. The fax management module realizes the management of fax jobs, processes the fax operation requests of the mail sending/receiving module, controls the fax call process through the interface, and obtains fax status notification messages. Inter-module communication interacts with the mail sending/receiving module; the call state machine module is responsible for maintaining the fax call process state machine, completing fax registration/logout, and fax incoming and outgoing calls through inter-process communication;

Media processing module: realize the mutual conversion between T.38 stream and fax file format; complete the control of media processing process and the interaction with media session information through inter-process communication with the call state machine module; RTP protocol deconstruction; RTP channel establishment /Remove, send and receive RTP stream;

Call control module: realize the encapsulation of the session initiation protocol stack, complete the construction and analysis of the session initiation protocol, establish and release the link with the peer end of the communication; use inter-process communication with the call state machine module to complete the call control process.

The present invention applies the above-mentioned IP facsimile device to send the method of facsimile:

In the first step, the mail sending/receiving module sends information to the fax control module, and the fax control module sends a confirmation message to the mail sending/receiving module after receiving the information, and at the same time requires the mail sending/receiving module to save the specific data storage location with the path name Given in the form, the fax control module sends a fax confirmation message to the mail sending/receiving module to indicate the fax image that needs to be sent to start processing and sending;

In the second step, the fax control module judges whether the fax transmission can be carried out. If it is judged as no, that is, the call state machine module is working at full capacity, then the sending fails, and the fax control module will notify the mail sending/receiving module to let the mail sending/receiving module Do retransmission; if it is judged to be yes, it will call the interface function of the call state machine module to generate a new fax session, and record the I address of the opposite end, the information of the opposite end, and the fax data path to be transmitted. ;

In the third step, the call control module sends a session initiation protocol message to the called party of the fax session, and the two parties perform a link connection, and complete the T.38 protocol version number, the maximum transmission rate when transmitting T.38 data, and whether to remove or Insert stuffing bits, perform capability conversion between linear format and MMR format, perform format conversion between linear format and JBIG format, negotiate information such as whether to generate training signals locally, and exchange information such as sending training signals and identification marks. After receiving the receiving confirmation sent by the called party, it can switch to the process of transmitting the media; at this time, the fax control module sends the fax signaling and fax images processed by the T.38 protocol through the media processing module, and communicates with the The called party of the fax session communicates and cuts off the link after the transmission is completed; during this process, if an error occurs, the fax control module will end the transmission and report the cause of the error to the mail sending/receiving module; if there is no If there is a sending error, the fax management module will report to the mail sending/receiving module that the sending is successful.

Preferably: the specific work of the fax management module of the present invention is as follows:

Step 1: The fax management module is blocked on the message queue,

Step 2: the fax management module gets the message from the message queue,

Step 3: whether the fax management module judges whether the message is valid, if it is judged to be yes, the fax management module passes the message to the call state machine module by calling the function of the driving state machine provided by the call state machine module; if it is judged to be no, it discards message and return to step 1;

Step 4: The fax management module gets the return value of the function, and sends a message to the corresponding module according to the return value of the function, and returns to step 1.

Preferably: the specific working method of the media processing module of the present invention is as follows:

Step 1): Select is a function that manages multiple messages, that is, a message collection; the Select call is blocked, and once a message is detected, the process is executed;

Step 2): the media processing module obtains a message, and judges the validity of the message, if it is judged to be yes, then finds the corresponding session according to the message sending target ID; if it is judged to be no, it returns to step 1); at the same time Judging whether the obtained message is creation information, judging that it is creating or releasing a dialogue, otherwise returning to step 1);

3) step: the media processing module judges the validity of the message in the read state, if it is judged to be yes, then call the interface function of the corresponding module, if it is judged to be no, then return to step 1);

The 4th) step: the media processing module judges whether to send a message, if it is judged to be yes, then send a message to the fax control module (41), and return to the 1st) step; if it is judged to be otherwise, directly return to the 1st) step.

The present invention adopts the above-mentioned technical scheme, and compared with the prior art, it has the following advantages: clear hierarchy, simple protocol, powerful function, support for multi-channel fax sessions, support for fax file forwarding mailboxes, support for source file fax transmission in multiple file formats, etc. .

1. The present invention is based on the SIP protocol, has the characteristics of the flexibility and scalability of the SIP protocol, and the protocol is simple.

2. The present invention can manage multiple faxes, and supports the function of forwarding received fax files (Tiff format) to user mailboxes, with more powerful functions.

3. The present invention has a virtual driver on the PC side, and supports word, pdf, and bmp format files to be converted into Tiff format and sent as a fax.

4. The present invention can support source file fax sending in various file formats.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the fax server module of the present invention.

FIG. 2 is a schematic diagram of Step 1 of sending a fax by the fax server module of the present invention.

FIG. 3 is a schematic diagram of Step 2 of sending a fax by the fax server module of the present invention.

FIG. 4 is a schematic diagram of Step 3 of sending a fax by the fax server module of the present invention.

Fig. 5 is the message format of the inter-process communication of the present invention.

Fig. 6 is the format of the function call transmission message of the present invention.

Fig. 7 is a flow diagram of the fax management module of the fax server module of the present invention.

Fig. 8 is a schematic flow chart of the media processing module of the fax server module of the present invention

FIG. 9 is a schematic diagram of the software architecture of the fax server module of the present invention.

Detailed ways

Below in conjunction with accompanying drawing technical scheme of the present invention is described in detail, as shown in Figure 1, the present invention comprises mail sending/receiving module 1, SIP facsimile equipment 2, back-to-back user agent 3, also comprises IP facsimile server 4, mail The control command port of the sending/receiving module 1 is connected to the IP fax server 4, and the IP fax server 4 will send feedback information to the mail sending/receiving module 1 after receiving it; the first output port of the IP fax server 4 is connected to the session initiation protocol fax device 2 The input terminal of the IP fax server 4 is connected to the input terminal of the back-to-back user agent 3 to realize the mutual conversion of the T.38 stream to the fax file format; the second output terminal of the IP fax server 4 is connected to the input terminal of the back-to-back user agent 3 to realize the encapsulation of the session initiation protocol stack;

The IP fax server 4 includes a fax control module 41, a media processing module 42, and a call control module 43;

The fax control module 41 includes a fax management module 411 and a call state machine module 412. The fax management module 411 realizes the management of the fax job, processes the fax operation request of the mail sending/receiving module 1, controls the fax call process through the interface, and also obtains the fax State notification messages, interact with the mail sending/receiving module 1 through inter-module communication; and the call state machine module 412 is responsible for maintaining the fax call process state machine, completing fax registration/logout, fax incoming and outgoing calls through inter-process communication;

Media processing module 42: realize the mutual conversion of T.38 stream to fax file format; communicate with the call state machine module 412 through inter-process communication, complete the control of the media processing process, and interact with the media session information; RTP protocol deconstruction; RTP Channel establishment/removal, RTP stream sending and receiving;

Call control module 43: realize the encapsulation of the session initiation protocol stack, can complete the construction and analysis of the session initiation protocol, and establish and release the link with the opposite end of the communication; use inter-process communication with the call state machine module 412 to complete Call control process.

The IP fax server 4 is the core part of the entire IP fax implementation, and the fax control module 41 is used as the main control module to manage the operation of the entire module and interact with other modules in the IP-PBX system. Secondly, the call control module 43 is used for managing the process of initiating a call and setting up a connection, realizing the dialing controlled by the SIP protocol under the IP environment, initiating processes such as connection, and managing the point-to-point IP facsimile transmission of one-to-many channels supported in the Fax Server module status of each channel. Finally, the T.30 and T.38 protocols will be implemented together to form a media control module to carry the signaling and image data to be sent in IP fax.

The mail sending/receiving module serves as an external interface of the fax server 4, and can realize the functions of sending and receiving mails, sending and receiving faxes, and managing them. The main functions are: processing external fax requests, sending fax requests to the fax server, and reporting the processing results to the outside according to the processing of fax requests by the fax server. It also provides the function of sending the fax to the user's mailbox after receiving it.

The following is the process that the mail sending/receiving module sends a request to the fax server through the internal protocol of the IP-PBX system, so as to realize the process of sending a fax.

In the first step, as shown in FIG. 2 , the fax control module 41 in the fax server module 4 is responsible for processing the messages sent by the mail sending/receiving module 1 . Fax control module 41 first can respond to the request of mail sending/receiving module 1, and sends back a confirmation message, and requires mail sending/receiving module 1 to provide the specific data storage location with the form of path name, after this, fax control module 41 Just send a fax confirmation message to the mail sending/receiving module 1 to indicate to start processing and sending the fax image that needs to be sent.

Second step, as shown in Figure 3, the facsimile control module 41 judges whether can carry out facsimile transmission, if its submodule call state machine 412 works at full capacity, then send failure, the facsimile control module 41 will notify mail sending/receiving module 1, let it do further processing. But most of the time it is successful, then it will call the interface function of the submodule call state machine 412 to generate a new state, and carry out the IP address of the opposite end, the information of the opposite end, and the fax data path to be transmitted, etc. Record.

In the third step, as shown in FIG. 4 , the facsimile process is completely handled by the facsimile control module 41 . First, it sends a SIP message to the opposite end through the call control module 43, and the two parties will connect the link and complete the negotiation of some necessary parameters. After that, the facsimile control module 41 considers that the link has been established, and can switch to the process of transmission media. At this time, the fax control module 41 sends the fax signal and fax image processed through the T.38 protocol through the media processing module 42, communicates with the opposite end, and cuts off the link after the transmission is completed. During this process, once an error occurs (such as the opposite end cannot be connected, etc.), the fax control module 41 will end this transmission and report the cause of the error to the mail sending/receiving module 1 . If everything goes well, the fax management module 411 will also report to the mail sending/receiving module 1 that the sending is successful.

In the above discussion, the transmission process is based on the good cooperation between modules. Modules may be implemented as separate processes, or as functions, so it is very important to define the format of message passing between modules. In the following, the communication format between modules is regulated, and for the communication between processes, the message format shown in Figure 5 is defined. Wherein, the number of the sending module and the number of the receiving module are the ID numbers of each module specified in advance, and the ID number of the message indicates what kind of message it is, and its specific content is given in the subsequent message content field. For the message delivery of the function type, the message format as shown in Figure 6 is defined: in this format, the state number corresponds to the state of each channel, the message ID specifies the type of message, and its content appears in the message content field.

In this way, the fax server 4 is divided into several sub-modules that are relatively clear and relatively independent in function according to the functions. The realization of each module can be relatively independent, and can be debugged one by one in the later stage debugging work, which can improve the efficiency of the entire development process.

The fax management module 411 is the control center of the entire fax server 4, plays an important role in the cooperation of other sub-modules, and is mainly responsible for receiving and sending messages. The main workflow shown in Figure 7 is as follows:

Step 1: The fax management module is blocked on the message queue,

Step 2: the fax management module gets the message from the message queue,

Step 3: whether the fax management module judges whether the message is valid, if it is judged to be yes, the fax management module passes the message to the call state machine module by calling the function of the driving state machine provided by the call state machine module; if it is judged to be no, it discards message and return to step 1;

Step 4: The fax management module gets the return value of the function, and sends a message to the corresponding module according to the return value of the function, and returns to step 1.

The media processing module 42 itself is implemented as a separate process. This process is blocked on a group of inter-process communication connections by the select system call of the Linux operating system standard. Once a message arrives, the process will resume execution. Because the main control module of the media processing module 42 is a media state control module , so it will be executed first. After the media state control module runs, it first obtains a complete message from the interface. The format of the message is also consistent with the unified format of inter-process communication. Then, it finds the structure of the corresponding session according to the target session ID in the message content, and then analyzes the In the state of the session, whether the received message is valid, because only certain types of messages can be accepted in a state, and it does not respond to other messages. If it is valid, the corresponding state transition will be generated, and the function provided by the submodule will be called. Corresponding processing is performed, and finally the message generated by the state transition is sent back in an inter-process communication standard message format through the inter-process communication connection with the fax control module 41 . Its complete processing flow is shown in Figure 8:

Step 1): The Select call is blocked, there is a message, and the process is executed; Select is a function that manages multiple messages, that is, a message set. Usually, if none of the message events in this message set occurs, the process that calls the Select function will be blocked all the time; until one or several message events in the message set occur, at this time, Select will wake up the process from the blocked state , and tell the process which message events have occurred, and the process can continue to execute and process these message events;

Step 2): the media processing module obtains a message, and judges the validity of the message, if it is judged to be yes, then finds the corresponding session according to the message sending target ID; if it is judged to be no, it returns to step 1); at the same time Judging whether the obtained message is creation information, judging that it is creating or releasing a dialogue, otherwise returning to step 1);

3) step: the media processing module judges the validity of the message in the read state, if it is judged to be yes, then call the interface function of the corresponding module, if it is judged to be no, then return to step 1);

Step 4): The media processing module judges whether it is necessary to send a message, if it is judged to be yes, it sends a message to the fax control module 41, and returns to the 1st) step; otherwise it directly returns to the 1st) step.

To sum up, according to the provisions of the T.30 protocol, the fax stage is mainly divided into five stages: call establishment, pre-message process, message process, post-message process, and call release, which are named A, B, and C, D, E five stages. Wherein the call setup stage is that the two ends of the transmission will initiate a call by the calling party, and the called party should respond. This process is similar to the process of establishing a conversation with a telephone, and it should be completed by the call control module 43, while the process before the message The three stages of , the process in the message, and the process after the message are unique to fax, including negotiation parameters, training channels, and transmission of fax data. The T.38 protocol has detailed regulations on these processes, so it should belong to the media processing module 42 to complete. The last stage, the call release stage, is a disconnection process, similar to the disconnection stage of an ordinary telephone, so it should be completed by the call control module 43 . The main process of sending a fax is as follows, assuming that everything goes smoothly and no errors occur:

1) The fax control module 41 sends a session creation message to the media processing module 42, informing it that a new session state is to be created. The media processing module 42 returns a message that the session is created successfully. Meanwhile, the state of the media processing module 42 will transition to the creation state, and the state of the fax control module 41 will change from the idle state to the fax initialization state. This stage belongs to the initialization stage and does not yet belong to any of the five stages of faxing.

2) send outgoing messages to the call control module 43 by the fax control module 41, and attach the information of the opposite end to be called, the whole process of calling is completed by the call control module 43, and the state in the fax control module 41 becomes the calling state simultaneously . After the process is accepted, the call control module 43 will report to the fax control module 41 that the call is successful and the link has been established. This process belongs to the A stage of faxing.

3) Send a message to the media processing module 42 by the fax control module 41, notify it to start voice playback, and at the same time pass the established link information to the media processing module 42, and simultaneously start a timer of 3 seconds, Used for timing. The media processing module 42 will play a section of dialing music to simulate the fax switching tone required for the traditional fax to switch from the telephone state to the fax state. At this time, the media processing module 42 is in the state of playing voice, and the fax control module 41 is still in the calling state. The process is still in Phase A.

4) After the dial tone is played, the opposite end will first switch to the fax mode, and the call control module 43 will obtain the information that the opposite end has switched, and report this information to the fax control module 41 . At this time, the fax control module 41 will send a message to the media processing module 42 to make it switch to the fax state, and the media processing module 42 will report a message that the state switching is successful. At this time, the media processing module 42 is in the state of obtaining ID information, and the fax control module 41 is in the stage of fax capability negotiation. Get started on the B-stage of faxing.

5) By the communication between the fax control module 41 and the opposite end, complete the tasks of three stages of B, C, and D. This process is all in charge of the fax control module 41, and after the process ends, report the sent message to the fax control module 41 . During this process, the fax control module 41 is always in the fax transmission state, and the media processing module 42 will go through stages such as information judgment, waiting for the peer to send, training, page transmission, data transmission end, and session end. When this process is over, Phase D is over.

6) The fax control module 41 sends a message to the call control module 43 to allow it to release the link, and at the same time sends a message to the media processing module 42 to allow it to release all the resources that have just been applied for in order to send a fax. This process is stage E. At this point, the facsimile process once completed is over.

The main process of receiving faxes is as follows (also assume that the process goes smoothly and no errors occur):

1) The call control module 43 first notifies the fax control module 41 that there is an incoming call from the opposite end by sending a message, and the fax control module 41 will consider that the call link is established and switch its state. From this process, proceed to Phase A.

2) The fax control module 41 sends a message to the media processing module 42, informing it to create a session. If the operation is performed successfully, the media processing module 42 will return a confirmation message, and make the fax control module 41 generate a state transition, and notify the call control Module 43 sends an acknowledgment signal indicating the establishment of the link. At this point, it is in stage A.

3) Send a message to the media processing module 42 by the call control module 43, notify it to start IP fax, and at the same time pass the established link information to the media processing module 42, let it play a section of dialing music, to simulate the traditional The facsimile switching tone required by the facsimile switching from the phone state to the facsimile state. At this time, the media processing module 42 is in the state of playing the voice. This process is timed, so it is not necessary for the media processing module 42 to notify the fax control module 41 after completion. The process is still in Phase A.

4) The facsimile control module 41 notifies the media processing module 42 to switch. At this time, both parties start parameter negotiation and training, etc., and the media processing module 42 reports the status in real time. This stage belongs to the B stage of fax.

5) The two parties communicate based on the T.38 protocol, and the media processing module 42 reports the status of the transmission. This stage mainly belongs to three stages B, C, and D.

6) The call control module 43 reports to the fax control module 41 that the other party hangs up, and the fax control module 41 performs a corresponding state switch, releases the link, and sends a message to notify the media processing module 42 to release resources. This process belongs to the E phase of faxing.

In the above process, it can be clearly seen that the fax control module 41 is the core of the entire fax process control, and it continuously sends various messages to the media processing module 42 and the call control module through its own state maintenance and state migration 43, making the two modules complete the corresponding functions, so as to complete the whole process of faxing in a coordinated manner.

The main function of the call control module 43 is to provide a simple and unified programming interface for upper-layer SIP applications. Provide functions such as call, hold, transfer, send/receive DTMF, etc. This module provides a unified call control protocol interface, which includes three types of commands: user commands, call commands, and control commands. Commands use a request/reply pattern.

The call control module 43 integrates the SIP protocol stack and the RTP protocol stack, and completes the management of the two protocol stacks through the control of the state machine, and maintains the state of a session. The SIP protocol is mainly used for session initiation and session confirmation, which can simulate the process of dialing up and initiating a connection on the PSTN network, and the RTP protocol stack is mainly used for voice bearer. Therefore, this module is divided into two modules according to the function, one mainly carries out calling and negotiation processes through the SIP protocol stack, and the other mainly carries out voice bearer through the RTP library function.

The call control module and the voice control module are responsible for calling the functions of the SIP protocol stack and the RTP protocol stack to communicate. In particular, the call control module also needs to maintain the session call state and communicate with the SIP application program through message transmission. The communication message must comply with the call control protocol, which includes three types of commands: user commands, call commands, and control commands. The specific main description is as follows:

User commands: This group of commands mainly includes two commands, login and logout, which can only be sent when using the call control module 43 . After a successful login, the user is online before logging out. Call and control commands are available only when you are online. Each connection can only have one user online at a time. A SIP application can establish multiple connections with the call control module. Login is used for user registration and login. At the same time of registration, sufficient resources are requested from the system, and activation registration is sent regularly after registration. Exit is used to log out the user and revoke the resources they requested.

Call command: This group of commands is mainly used to initiate a call, establish a connection, hang up and other operations, and can be sent and received. Initiating a call must be the first command of the call, which needs to specify a globally unique call-id to identify the call. The command to initiate a call can be initiated by a SIP application, at this time, the SIP application is the calling party; or initiated by the call control module, at this time, the SIP application is the called party. The establish connection command can only be initiated when the call is established or ringing, and the call is in the connected state after answering. Hang up command can be initiated in any state, except idle state, to terminate a call.

Control commands: This group of commands mainly plays a role in controlling the conversation. The control commands include four commands: HOLD, REFER, AUDIO, and DTMF. For modules using CCM, HOLD and AUDIO can only be sent, while REFER and DTMF can be sent and received. Note that control commands do not change the call state. The HOLD command is the hold/retrieve command. If sid is specified, only the specified sid is reserved, otherwise all sids are reserved. The REFER command is a call transfer command. Both AUDIO commands and DTMF commands are voice control commands, which will change the voice transmission mode of the CCM module.

The above command is also a message that the SIP user can send to the call control module, and the message has a fixed format.

The call control module 43 has 9 kinds of states, which are idle (IDLE) state, initiating call (INVITING) state, call establishment (INVITED) state, acceptance (ACCEPTED) state, ringing (RINGING) state, call transfer (OFFERING) state, respectively. ) status, CONNECTED status, TERMINATING status, TERMINATED status.

The implementation of the voice service module is relatively simple, and its state only has two states of playing voice and closing voice, and its state is controlled by the call control module. After the link is set up, the call control module will send a message (its format is the same as the command format described above) to the voice service module to allow it to perform mode switching and enter the playing voice state. After the link is disconnected, its The voice service module will also be notified to switch the state to the voice off state.

As shown in Figure 9, the specific effects of each process and thread of the present invention are as follows:

Call control module process: mainly responsible for the establishment of the link with the opposite end, etc., which implements the content of the SIP protocol, and is the bearer of functions such as initiating calls and accepting incoming calls.

Media processing module process: This process mainly implements the T.30, T.4 and T.38 protocols, and is responsible for the actual signaling and data transmission during the facsimile process, which can be said to be the core responsible for the actual transmission.

TCP server thread: Responsible for communicating with the mail sending/receiving module, monitoring the message sending and receiving with the mail sending/receiving module, and sending formatted messages to the message queue.

Call processing module TCP client thread: responsible for communicating with the call processing module, monitoring the message sending and receiving with the call processing module, and sending formatted messages to the message queue.

Media TCP client thread: responsible for communicating with the media processing module, monitoring the sending and receiving of messages with the media processing module, and sending formatted messages to the message queue.

Fax Control main thread: responsible for processing messages in the message queue, and realizing the functions defined for the fax management module and call state machine.

Figure 9 shows the software architecture of a complete fax server module. The architecture implements this module as three separate processes.

First of all, the fax control module process is the core of this module, which is composed of two modules, the fax management module and the call state machine, which are in charge of the status and information of the entire fax. Since the two modules of the fax management module and the call state machine are very closely related to each other, and the real-time requirements of the communication are very high, so we synthesized them into a process to realize, although this partly destroys the module's Independence and simplicity of module division, but it can get huge performance improvements, so it is still very sensible. This process has a message queue, which is used to collect messages sent by other processes, analyze them, and then trigger the processing of the fax management module and the corresponding state changes in the call state machine. At the same time, the processes connected with other processes The inter-communication connection sends out the work it needs to be done by other modules in the form of fixed-format messages. For example, now in the message queue is the connection establishment complete message sent by the call control module, the fax control module accepts this message, and generates a corresponding state switch, and finally sends a message through the inter-process communication connection established with the media processing module, so that The media processing module proceeds to the next step. If other processes do not send messages to the fax management module, they will be stuck in the message queue until there are new messages to be processed. The facsimile control module process also includes three sub-threads. The tasks of these three sub-threads are very simple. It is to constantly monitor whether there is a message that meets the specified format on the inter-process communication connection established with other processes. Posted to the message queue, processed by the main thread of the fax management module. The reason for needing these three threads is that they can be blocked on each inter-process communication connection, and then deliver the message to the message queue when there is a real message, without the need for the main thread to be in a blocked state all the time to continuously monitor the three threads. An inter-process communication connection, which increases efficiency.

Secondly, the call control module will be implemented as a separate process, which is mainly responsible for establishing a connection with the remote end. There are mainly two ways to communicate with other processes. First, if it has a message to report to the process of the fax control module, it sends the message to be sent to the fax control module through the message queue. After receiving the message, the fax control module will deal with it accordingly. Second, the call control module can obtain the tasks required by the fax control module through inter-process communication connection with the fax control.

Finally, implement the media processing module as an independent media processing module process. Protocols such as T.30, T.38 and T.4 are implemented in this process. This process is also similar to the above call control module process. On the one hand, it sends messages to the fax control module process through the message queue, and continuously monitors and faxes the control module. The inter-process communication connection that the module processes are connected to complete the work assigned to it by the fax control module process.

Claims (4)

1. A kind of IP facsimile device, comprise mail sending/receiving module (1), SIP facsimile equipment (2), back-to-back user agent (3), it is characterized in that: also comprise IP fax server (4), mail sends The control command port of the/receiving module (1) is connected with the IP fax server (4), and the IP fax server (4) will send feedback information to the mail sending/receiving module (1) after receiving it; the first IP fax server (4) The output end is connected with the input end of the session initiation protocol fax device (2), and the mutual conversion from the T.38 stream to the fax file format is realized; the second output end of the IP fax server (4) is connected with the back-to-back user agent (3) The input terminal is connected to realize the encapsulation of the session initial protocol stack; The IP fax server (4) includes a fax control module (41), a media processing module (42), and a call control module (43); The fax control module (41) includes a fax management module (411) and a call state machine module (412). The fax management module (411) realizes the management of fax operations, processes the fax operation request of the mail sending/receiving module (1), and passes While the interface controls the fax call process, it also obtains fax status notification messages, and interacts with the mail sending/receiving module (1) through inter-module communication; and the call state machine module (412) is responsible for maintaining the fax call process state machine, and through inter-process communication Complete fax registration/deregistration, incoming and outgoing fax calls; Media processing module (42): realize the mutual conversion of T.38 stream to fax file format; communicate with the call state machine module (412) through inter-process communication, complete the control of media processing process, and the interaction of media session information; RTP Protocol deconstruction; RTP channel establishment/removal, RTP stream sending and receiving; Call control module (43): realize the encapsulation of the session initiation protocol stack, can complete the construction and analysis of the session initiation protocol, and establish and release the link with the opposite end of the communication; use the process with the call state machine module (412) Inter-communication to complete the call control process. 2. A method for sending a fax by an IP fax device according to claim 1, characterized in that: The first step, the mail sending/receiving module (1) sends information to the fax control module (41), and the fax control module (41) sends a confirmation message to the mail sending/receiving module (1) after receiving the information, and requires the mail to send /receiving module (1) provides the specific data storage location with the form of path name, and the fax control module (41) just sends a fax confirmation message to the mail sending/receiving module (1) to indicate that it starts to process and send what needs to be sent Fax image; In the second step, the fax control module (41) judges whether fax transmission can be carried out, if it is judged as no, that is, the call state machine module (412) is working at full capacity, and then fails to send, and the fax control module (41) will notify the mail to send/ The receiving module (1) allows the mail sending/receiving module (1) to resend; if it is judged to be yes, then it will call the interface function of the call state machine module (412) to generate a new fax session all the way, and the IP address of the opposite end The address and peer information, as well as the fax data path to be transmitted, etc. are all recorded; In the third step, the call control module (43) sends the session initiation protocol message to the called party of the facsimile session, and both parties carry out the link connection, and complete the T.38 protocol version number, the maximum transmission rate when transmitting the T.38 data, and the process C Whether to remove or insert padding bits, perform capability conversion between linear format and MMR format, perform format conversion between linear format and JBIG format, negotiate information such as whether to generate training signals locally, and send information such as training signals and identification marks interact. After receiving the receiving confirmation sent by the called party, the facsimile control module (41) thinks that the link has been established, and can switch to the process of transmitting the medium; ) send fax signaling and fax images processed by the T.38 protocol, communicate with the called party of the fax session, and cut off the link after the transmission is completed; during this process, if an error occurs, the fax control module (41) Will end this transmission, and report the reason of the error to the mail sending/receiving module (1); if there is no sending error, the fax management module (411) will report this sending success to the mail sending/receiving module (1). 3. the method for IP fax device sending fax according to claim 2, is characterized in that: the specific work of fax management module (411) is as follows: Step 1: The fax management module is blocked on the message queue, Step 2: the fax management module gets the message from the message queue, Step 3: whether the fax management module judges whether the message is valid, if judged as yes, the fax management module passes the message to the call state machine module (412) by calling the function of the drive state machine provided by the call state machine module; if judged as no , discard the message and return to step 1; Step 4: The fax management module gets the return value of the function, and sends a message to the corresponding module according to the return value of the function, and returns to step 1. 4. The method for sending a fax by an IP fax device according to claim 2, characterized in that: The concrete work method of media processing module (42) is as follows: Step 1): Select is a function that manages multiple messages, that is, a message collection; the Select call is blocked, and once a message is detected, the process is executed; 2nd) step: the media processing module (42) obtains a message, and judges the validity of the message, if it is judged to be yes, then find the corresponding session according to the message sending target ID; if it is judged to be no, then return to the first) Step; Judging whether the obtained message is the creation information simultaneously, judging as creating or releasing a dialogue, judging otherwise returning to step 1); 3) step: the media processing module judges the validity of the message in the read state, if it is judged to be yes, then call the interface function of the corresponding module, if it is judged to be no, then return to step 1); The 4th) step: the media processing module judges whether to send a message, if it is judged to be yes, then send a message to the fax control module (41), and return to the 1st) step; if it is judged to be otherwise, directly return to the 1st) step.

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