RFC requires a port for Host when it is non default. https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.23

wnemay · wnemay · commit 4f55c36c80d2 · 2016-04-30T15:46:19.000-07:00
diff --git a/src/WebSocketsClient.cpp b/src/WebSocketsClient.cpp
@@ -392,7 +392,7 @@ void WebSocketsClient::sendHeader(WSclient_t * client) {
 #endif
 
     String handshake =  "GET " + client->cUrl + " HTTP/1.1\r\n"
-                        "Host: " + _host + "\r\n"
+                        "Host: " + _host + ":" + _port + "\r\n"
                         "Upgrade: websocket\r\n"
                         "Connection: Upgrade\r\n"
                         "User-Agent: arduino-WebSocket-Client\r\n"
@@ -620,6 +620,3 @@ void WebSocketsClient::asyncConnect() {
 }
 
 #endif
-
-
-
