[Turn] Exosip2-5.1.0 TCP transmission method use excerpt

1. Random problem with the port used to send messages using TCP
  : The port is not fixed when using exosip2 to actively send TCP messages;
code analysis:
  First, there are two sources of sock for sending data in TCP mode in exoisp2 (eXtl_tcp.c):

"1", the sockets returned by the accept function in the tcp_tl_read_message function, up to 200;

This is a passive connection as a server, and the returned port number of the sock binding is set by us with eXosip_listen_addr;

"2", the newly established socket when the TCP connection is initiated actively;

Create a new socket in _tcp_tlconnect_socket but there is an if judgment to decide whether to perform port binding, the judgment is as follows:

If there is no port binding, a port number will be randomly selected, which is the problem.

The setting of ai_addr_len in the judgment condition is set in tcp_tl_open, but there is a macro that controls it, which is undefined by default, as follows:

So if the macro is turned on, we can use the port number we set to send data, but the function of the macro ENABLE_MAIN_SOCKET is not mentioned, so I don’t know what effect it will have after it is turned on. eXtl_tls.c says to prevent insecure tls connections, and it feels like it has nothing to do with tcp.

2. Additional settings
  need to set the sock in eXtl_tcp.c to SO_REUSEADDR, and then add SO_REUSEPORT on this basis, otherwise the sock for sending the message will fail to be created.

setsockopt (sock, SOL_SOCKET, SO_REUSEPORT, (void *) &valopt, sizeof (valopt));
1
3、结果：

————————————————
Copyright statement: This article is the original article of the CSDN blogger "King log", and it follows the CC 4.0 BY-SA copyright agreement. Please attach the original source link and the copy statement.
Original link: https://blog.csdn.net/fpgatom/article/details/98090458