CN106470252B - Method for querying IP address by application program and communication terminal - Google Patents

Abstract

The invention provides a method for inquiring an IP address by an application program and a communication terminal. The method for inquiring the IP address by the application program comprises the following steps: the application program sends inquiry information to a DNS (domain name server) by using UDP (user Datagram protocol) to inquire the IP address of the host name of the website; receiving a DNS response packet sent by the DNS server in response to the query information; judging whether the DNS response packet is truncated or not; when the DNS reply packet is truncated, attempting to connect to the DNS server using TCP; judging whether the DNS server is successfully connected by using TCP; attempting to access a secondary DNS server using UDP when connecting the DNS server using the TCP fails; determining whether accessing the secondary DNS server using UDP is successful; and returning the IP address to the application program when the auxiliary DNS server is successfully accessed by using UDP. The invention improves the success probability of IP address query.

Description

Method for querying IP address by application program and communication terminal

technical field

The invention relates to the field of communications, in particular to a method for querying an IP address by an application program and a communication terminal.

Background technique

The Domain Name System (DNS) uses the User Datagram Protocol (UDP) for transmission by default. Nowadays, various websites often use multiple servers for load balancing, and the hostname of this website corresponds to multiple IP addresses. When an application installed on a DNS client (for example, an Android phone) needs to query the IP address of a website hostname, a recursive query is usually used. At this time, the DNS response (answer) packet sent by the DNS server in response to the recursive query is too large, so it is easy to exceed the carrying capacity of the UDP. When the DNS reply packet exceeds 512 bytes, the excess part will be truncated. When the DNS client receives the truncated DNS response packet, it will try to connect to the DNS server using Transmission Control Protocol (TCP). When connecting to the DNS server through TCP, it is not limited by the size of the response packet. However, in the prior art, many DNS servers will refuse the TCP connection. When neither UDP nor TCP is used to obtain the IP address from the DNS server, the application program of the DNS client will query the secondary DNS server through TCP to obtain the IP address, while in the prior art, the application program of the DNS client will query the secondary DNS server through TCP. The secondary DNS server will not be successfully queried, and the IP address will not be obtained.

SUMMARY OF THE INVENTION

The present invention provides a method for an application program to query an IP address, and the method for an application program to query an IP address includes:

The application uses UDP to send query information to the DNS server to look up the IP address of the website hostname;

receiving a DNS response packet sent by the DNS server in response to the query information;

Determine whether the DNS response packet is truncated;

When the DNS response packet is truncated, use TCP to try to connect to the DNS server;

Determine whether using TCP to connect to the DNS server is successful;

When using the TCP to connect to the DNS server fails, use UDP to try to access the secondary DNS server;

determining whether access to the secondary DNS server using UDP was successful; and

When accessing the secondary DNS server using UDP is successful, the IP address is returned to the application.

Wherein, the method for the application to query the IP address further includes:

When using UDP to access the auxiliary DNS server is unsuccessful, use UDP to try to access the DNS server according to the truncated DNS response packet;

Determine whether the truncated DNS response packet contains an IP address;

When the truncated DNS response packet contains an IP address, the IP address is obtained from the truncated DNS response packet, and the IP address is returned to the application.

Wherein, the method for the application to query the IP address further includes:

When the truncated DNS response packet does not contain an IP address, the application program is prompted to fail to query the IP address.

Wherein, the method for the application to query the IP address includes:

When the DNS response packet is not truncated, the IP address is obtained from the DNS response packet, and the IP address is returned to the application.

Wherein, the step "judging whether the DNS response packet is truncated" includes:

Read the number of the flag bit in the DNS response packet;

Determine whether the number of the flag bit in the DNS response packet is 1; and

When the number of the flag bit in the DNS response packet is 1, the DNS response packet is truncated; otherwise, the DNS response packet is not truncated.

Compared with the prior art, when the method for querying the IP address of an application program of the present invention fails to connect to the DNS server through the TCP, the method of UDP is used to try to access the auxiliary DNS server. In the prior art, when the connection to the DNS server through the TCP fails, the auxiliary DNS server is queried by switching to the TCP. However, using the TCP method to query the DNS auxiliary server conflicts with the protocols supported by the DNS auxiliary server, which increases the probability of failure of the IP address query. The default protocol supported by the DNS auxiliary server is UDP, that is, the DNS auxiliary server supports query in UDP mode. Therefore, in the present invention, when the connection to the DNS server through the TCP fails, the UDP method is used to try to access the auxiliary DNS server, which improves the probability of the IP address query being successful.

The present invention also provides a communication terminal, the communication terminal includes:

The query module is used to send query information to the DNS server using UDP to query the IP address of the website host name;

a receiving module, receiving a DNS response packet sent by the DNS server in response to the query information;

The first judgment module is used for judging whether the DNS response packet is truncated;

a connection module, used for trying to connect to the DNS server using TCP when the DNS response packet is truncated;

The second judging module is used for judging whether the use of TCP to connect the DNS server is successful;

The first access module is used to use UDP to try to access the secondary DNS server when the connection to the DNS server using the TCP fails;

A third judging module for judging whether using UDP to access the auxiliary DNS server is successful; and

The address returning module is configured to return the IP address to the application when the auxiliary DNS server is accessed successfully by using UDP.

Wherein, the communication terminal further includes:

A second access module, configured to use UDP to attempt to access the DNS server according to the truncated DNS response packet when accessing the secondary DNS server using UDP is unsuccessful; and

The fourth judgment module is used for judging whether the truncated DNS response packet contains an IP address;

Wherein, the address returning module is further configured to obtain the IP address from the truncated DNS response packet when the truncated DNS response packet contains an IP address, and return the IP address to the application program.

Wherein, the communication terminal further includes:

The address query failure module is used to prompt the application program to fail to query the IP address when the truncated DNS response packet does not contain an IP address.

Wherein, the address return module is further configured to obtain an IP address from the DNS response packet when the DNS response packet is not truncated, and return the IP address to the application program.

Wherein, the first judgment module further includes:

A reading submodule is used to read the number of the flag bit in the DNS response packet;

Judging submodule for judging whether the number of the flag bit in the DNS response packet is 1; and

The determining submodule is configured to determine that the DNS response packet is truncated when the number of the flag bit in the DNS response packet is 1; otherwise, determine that the DNS response packet is not truncated.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a flowchart of a method for an application to query an IP address in a preferred embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a communication terminal in a preferred embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a communication terminal in another preferred embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

It should be noted that the terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. As used in the embodiments of the present invention and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

The method for querying an IP address by an application program is applied to a communication terminal, and is used for querying the IP address corresponding to the hostname of a website. The communication terminal can be, but is not limited to, an Android smart phone with a communication function, an Internet device (Mobile Internet Device, MID), an e-book, a portable playback station (Play Station Portable, PSP) or a Personal Digital Assistant (Personal Digital Assistant, PDA) ) and other portable electronic devices. The method for the application to query the IP address includes but is not limited to the following steps.

Step S101, the application sends query information to the DNS server by using UDP to query the IP address of the website host name. Wherein, the application program is an application program installed on the communication terminal.

Step S102: Receive a DNS response packet sent by the DNS server in response to the query information. When the application uses UDP to send query information to the DNS server, the DNS server will respond to the query information and send out a DNS response packet.

Step S103, judging whether the DNS response packet is truncated. Since the DNS server uses a recursive query method to correspond to the query information, the use of the recursive query method will cause the DNS response packet to be too large, thus easily exceeding the carrying capacity of the UDP. When the DNS reply packet exceeds 512 bytes, the excess part will be truncated. When the DNS response packet is truncated, go to step S104; when the DNS response packet is not truncated, go to step S113.

Specifically, in this embodiment, the step S103 includes the following steps.

Step 1, read the number of the flag bit in the DNS response packet.

Step II, judging whether the number of the flag bit in the DNS response packet is 1.

Step III, when the number of the flag bit in the DNS response packet is 1, the DNS response packet is truncated; otherwise, the DNS response packet is not truncated.

When the DNS response packet is truncated, the flag bit in the DNS response packet will be marked as 1 to indicate that the DNS response packet is truncated. Therefore, whether the DNS response packet is truncated can be judged by the number of the flag bit in the DNS response packet.

Step S104, when the DNS response packet is truncated, use TCP to try to connect to the DNS server. In this step, when the DNS response packet is truncated, TCP is used to try to connect to the DNS server. When trying to connect to the DNS server through TCP, the response packet generated by the DNS server in response to the query information in the TCP mode has no size limit.

Step S105, it is judged whether the connection to the DNS server using TCP is successful. When the connection to the DNS server using TCP fails, the process proceeds to step S106; when the connection to the DNS server using TCP is successful, the process proceeds to step S114.

Step S106, when using the TCP to connect to the DNS server fails, use UDP to try to access the secondary DNS server. In this step, when the connection to the DNS server through the TCP fails, an attempt is made to access the secondary DNS server in a UDP manner. In the prior art, when the connection to the DNS server through the TCP fails, the auxiliary DNS server is queried by switching to the TCP. However, using the TCP method to query the DNS auxiliary server conflicts with the protocols supported by the DNS auxiliary server, which increases the probability of failure of the IP address query. The default protocol supported by the DNS auxiliary server is UDP, that is, the DNS auxiliary server supports query in UDP mode. Therefore, in this step, when the connection to the DNS server through the TCP fails, an attempt is made to access the auxiliary DNS server by means of UDP, which increases the probability of the IP address query being successful.

Step S107, judging whether using UDP to access the auxiliary DNS server is successful. When using UDP to access the auxiliary DNS server is successful, go to step S108; when using UDP to access the auxiliary DNS server is unsuccessful, go to step S109.

Step S108, when using UDP to access the secondary DNS server successfully, return the IP address to the application.

Step S109, when using UDP to access the secondary DNS server is unsuccessful, try to access the DNS server by using UDP according to the truncated DNS response packet.

Step S110, judging whether the truncated DNS response packet contains an IP address. When the truncated DNS response packet contains an IP address, the process proceeds to step S111; when the truncated DNS response packet does not contain an IP address, the process proceeds to step S112.

Step S111, when the truncated DNS response packet contains an IP address, obtain the IP address from the truncated DNS response packet, and return the IP address to the application.

Although the IP address in the truncated DNS response packet is truncated and incomplete, the truncated DNS response packet still includes some IP addresses. In the prior art, when the DNS client receives the truncated DNS When responding to the packet, the IP address in the truncated DNS response packet will be ignored, and instead it will try to connect to the DNS server using TCP, which greatly reduces the probability of the DNS server being successfully accessed. In the present invention, when the DNS server is attempted to be accessed using UDP according to the truncated DNS response packet, the probability of the DNS server being accessed successfully can be improved.

Step S112, when the truncated DNS response packet does not contain an IP address, prompt the application program to fail in querying the IP address.

Step S113, when the DNS response packet is not truncated, obtain an IP address from the DNS response packet, and return the IP address to the application.

Step S114, when the connection to the DNS server using TCP is successful, the IP address is returned to the application.

The communication terminal of the present invention is described below in conjunction with the description of the method for querying an IP address by an application program of the present invention. Please refer to FIG. 2 , which is a schematic structural diagram of a communication terminal in a preferred embodiment of the present invention. The communication terminal may be, but is not limited to, a portable electronic device such as an Android smart phone with a communication function, an Internet device, an e-book, a portable playback station, or a personal digital assistant. The communication terminal 10 is installed with an application program, and the application program can query the IP address corresponding to the host name of the website. The communication terminal 10 includes but is not limited to a query module 101 , a receiving module 102 , a first judgment module 103 , a connection module 104 , a second judgment module 105 , a first access module 106 , a third judgment module 107 and an address return module 108 . The functions of each module are described in detail as follows.

The query module 101 is configured to use UDP to send query information to the DNS server to query the IP address of the website host name.

The receiving module 102 receives a DNS response packet sent by the DNS server in response to the query information.

The first judging module 103 is configured to judge whether the DNS response packet is truncated.

In this embodiment, the first determination module 103 further includes a reading sub-module 1031 , a determination sub-module 1032 and a determination sub-module 1033 . The specific functions of each sub-module are introduced as follows.

The reading sub-module 1031 is used to read the number of the flag bit in the DNS response packet.

The judging submodule 1032 is configured to judge whether the number of the flag bit in the DNS response packet is 1.

The determination sub-module 1033 is configured to determine that the DNS response packet is truncated when the number of the flag bit in the DNS response packet is 1; otherwise, determine that the DNS response packet is not truncated.

The connection module 104 is configured to use TCP to attempt to connect to the DNS server when the DNS response packet is truncated.

The second judging module 105 is used for judging whether the connection to the DNS server using TCP is successful.

The first access module 106 is configured to use UDP to attempt to access the secondary DNS server when the connection to the DNS server using the TCP fails.

The third judging module 107 is used for judging whether using UDP to access the auxiliary DNS server is successful.

The address returning module 108 is configured to return the IP address to the application program when using UDP to access the secondary DNS server successfully.

In this embodiment, the communication terminal 10 further includes a second access module 109 and a fourth judgment module 110 . The second access module 109 is configured to use UDP to attempt to access the DNS server according to the truncated DNS response packet when accessing the secondary DNS server using UDP is unsuccessful; and

The fourth judging module 110 is used for judging whether the truncated DNS response packet contains an IP address.

The address returning module 108 is further configured to obtain the IP address from the truncated DNS response packet when the truncated DNS response packet contains an IP address, and return the IP address to the application program.

In this embodiment, the communication terminal 10 further includes an address query failure module 111 .

The address query failure module 111 is configured to prompt the application program to fail to query the IP address when the truncated DNS response packet does not contain an IP address.

In this embodiment, the address returning module 108 is further configured to obtain an IP address from the DNS response packet when the DNS response packet is not truncated, and return the IP address to the application program.

Please refer to FIG. 3 , which is a schematic structural diagram of a communication terminal in another preferred embodiment of the present invention. The mobile terminal 70 is installed with an application program, and the application program can query the IP address corresponding to the host name of the website. The mobile terminal 70 may include: at least one processor 701 , such as a central processing unit (CPU), at least one network interface 704 , user interface 703 , memory 705 , at least one communication bus 702 and display screen 706 . Among them, the communication bus 702 is used to realize the connection and communication between these components. The user interface 703 may include a display screen (Display) 706, and the optional user interface 703 may also include a standard wired interface and a wireless interface. Optionally, the communication interface 704 may include a standard wired interface (eg, a data cable interface, a network cable interface, etc.), a wireless interface (eg, a WI-FI interface, a Bluetooth interface, a near field communication interface). The memory 705 may be a high-speed random access memory (RAM), or a non-volatile memory (non-volatile memory), such as at least one disk memory. The memory 705 can optionally also be at least one storage device located away from the aforementioned processor 701 . As shown in FIG. 3 , the memory 705 as a computer storage medium may include an operating system, a network communication module, a user interface module, and a program for a method of querying an IP address.

In the mobile terminal 70 shown in FIG. 3, the processor 701 can be used to call the program for querying the IP address stored in the memory 705, and perform the following operations:

The application uses UDP to send query information to the DNS server to look up the IP address of the website hostname.

A DNS response packet sent by the DNS server in response to the query information is received. Determine whether the DNS response packet is truncated.

When the DNS reply packet is truncated, try to connect to the DNS server using TCP.

Determine whether the connection to the DNS server using TCP is successful.

When the connection to the DNS server using the TCP fails, an attempt is made to access the secondary DNS server using UDP.

Determine whether accessing the secondary DNS server using UDP is successful.

When accessing the secondary DNS server using UDP is successful, the IP address is returned to the application.

When accessing the secondary DNS server using UDP is unsuccessful, using UDP attempts to access the DNS server according to the truncated DNS response packet.

Determine whether the truncated DNS response packet contains an IP address.

When the truncated DNS response packet contains an IP address, the IP address is obtained from the truncated DNS response packet, and the IP address is returned to the application.

When the truncated DNS response packet does not contain an IP address, the application program is prompted to fail to query the IP address.

When the DNS response packet is not truncated, the IP address is obtained from the DNS response packet, and the IP address is returned to the application.

When the connection to the DNS server using TCP is successful, the IP address is returned to the application.

Specifically, in this embodiment, the processor 701 invokes the program of the query IP method stored in the memory 705, and performs the operation of judging whether the DNS response packet is truncated, including:

Read the number of the flag bit in the DNS response packet;

Determine whether the number of the flag bit in the DNS response packet is 1;

When the number of the flag bit in the DNS response packet is 1, the DNS response packet is truncated; otherwise, the DNS response packet is not truncated.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing the relevant hardware through a computer program. The flight mode enabling program can be stored in a computer-readable storage medium. During execution, the processes of the embodiments of the above-mentioned methods may be included. The storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM), or a random access memory (Random Access Memory, RAM) or the like.

The above disclosures are only one or more preferred embodiments of the present invention. The principles and implementations of the present invention are described by specific examples herein. The descriptions of the above embodiments are only used to help understand the present invention. method and its core idea; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation and application scope. Invention limitations.

Claims (12)

1. a method for querying an IP address by an application program, wherein the method for querying an IP address by the application program comprises: The application uses UDP to send query information to the DNS server to look up the IP address of the website hostname; receiving a DNS response packet sent by the DNS server in response to the query information; Determine whether the DNS response packet is truncated; When the DNS response packet is truncated, use TCP to try to connect to the DNS server; Determine whether using TCP to connect to the DNS server is successful; When using the TCP to connect to the DNS server fails, use UDP to try to access the secondary DNS server; determining whether access to the secondary DNS server using UDP was successful; and When accessing the secondary DNS server using UDP is successful, the IP address is returned to the application. 2. The method for querying an IP address by an application program as claimed in claim 1, wherein the method for querying an IP address by the application program further comprises: When using UDP to access the auxiliary DNS server is unsuccessful, use UDP to try to access the DNS server according to the truncated DNS response packet; Determine whether the truncated DNS response packet contains an IP address; When the truncated DNS response packet contains an IP address, obtain the IP address from the truncated DNS response packet, and return the IP address to the application. 3. The method for querying an IP address by an application program as claimed in claim 2, wherein the method for querying an IP address by the application program further comprises: When the truncated DNS response packet does not contain an IP address, the application program is prompted to fail to query the IP address. 4. The method for querying an IP address by an application program as claimed in claim 1, wherein the method for querying an IP address by the application program comprises: When the DNS response packet is not truncated, the IP address is obtained from the DNS response packet, and the IP address is returned to the application. 5. The method for querying an IP address by an application program as claimed in claim 1, wherein the step "judging whether the DNS response packet is truncated" comprises: Read the number of the flag bit in the DNS response packet; Determine whether the number of the flag bit in the DNS response packet is 1; and When the number of the flag bit in the DNS response packet is 1, the DNS response packet is truncated; otherwise, the DNS response packet is not truncated. 6. A communication terminal, wherein the communication terminal comprises: The query module is used to send query information to the DNS server using UDP to query the IP address of the website host name; a receiving module, receiving a DNS response packet sent by the DNS server in response to the query information; The first judgment module is used for judging whether the DNS response packet is truncated; a connection module, used for trying to connect to the DNS server using TCP when the DNS response packet is truncated; The second judging module is used for judging whether the use of TCP to connect the DNS server is successful; The first access module is used to use UDP to try to access the secondary DNS server when the connection to the DNS server using the TCP fails; A third judging module for judging whether using UDP to access the auxiliary DNS server is successful; and The address returning module is configured to return the IP address to the application when the auxiliary DNS server is successfully accessed by using UDP. 7. The communication terminal according to claim 6, wherein the communication terminal further comprises: a second access module, configured to use UDP to attempt to access the DNS server according to the truncated DNS response packet when accessing the secondary DNS server using UDP is unsuccessful; and The fourth judgment module is used for judging whether the truncated DNS response packet contains an IP address; Wherein, the address returning module is further configured to obtain the IP address from the truncated DNS response packet when the truncated DNS response packet contains an IP address, and return the IP address to the application program. 8. The communication terminal according to claim 7, wherein the communication terminal further comprises: The address query failure module is used to prompt the application program to fail to query the IP address when the truncated DNS response packet does not contain an IP address. 9. The communication terminal according to claim 6, wherein the address return module is further configured to obtain an IP address from the DNS response packet when the DNS response packet is not truncated, and return the DNS response packet to the The IP address is returned to the application. 10. The communication terminal according to claim 6, wherein the first judgment module further comprises: A reading submodule is used to read the number of the flag bit in the DNS response packet; Judging submodule for judging whether the number of the flag bit in the DNS response packet is 1; and A determination sub-module, configured to determine that the DNS response packet is truncated when the number of the flag bit in the DNS response packet is 1; otherwise, determine that the DNS response packet is not truncated. 11. A computer-readable storage medium, characterized in that, the computer-readable storage medium stores a computer program, and the computer program is used to instruct relevant hardware to complete any one of claims 1 to 5. method described. 12. A mobile terminal, comprising: a memory and at least one processor; the processor is configured to invoke a program for querying an IP address stored in the memory to execute the method of any one of claims 1 to 5.