1. Author: Gong Han
2. Client
   1. buildsocket
      1. pthread_attr_init
      2. define struct sockaddr_in
      3. $sockfd = socket
      4. check ip
      5. pthread_attr_setdetachstate
      6. pthread_create(recv_func)
         1. recvfrom($sockfd)
         2. gtkprintf($msg_recv)
      7. pthread_attr_destroy
      8. close
   2. send_text
      1. sendto($sockfd, $msg_send)
3. Server
   1. define struct sockaddr_in
   2. pthread_attr_init
   3. $sockfd = socket
   4. bind
   5. pthread_attr_setdetachstate
   6. pthread_create(recv_func)
      1. recvfrom($sockfd)
      2. printf($msg_recv)
   7. pthread_attr_destroy
   8. send_func
      1. fgets($msg_send)
      2. sendto($sockfd, $msg_send)
   9. close