如何在服务器上的线程和客户端上的线程之间同步？

Question

My application creates threads for file transfer on both the server and client sides. Right now I'm using delaying tactics (a simple for loop) on client side so that thread creation in client is done after the thread creation process in server.

The app works fine. But this is crude, if not ugly. I need to find a technical way so that the client thread is not started until it knows that server thread has been started.

I tried to use a send() from server to the client. The client's recv() must block for server's signal but apparently it doesn't. The message on the client console is about connection being refused by the server. Any hints, please?

Answer 1

select() may be what you're looking for: you give it a set of sockets and it blocks until something happens on these sockets (and you can provide a timeout to avoid waiting forever).
Call select() to wait until data is received on the client side, then recv() to ensure what was received is the right message from the server.

Answer 2

Seems you use connectionless transport. In this case I would suggest playing ping-pong game, client sends "ping" udp packet to server in loop (with reasonable period) until client receives "pong" UDP packet from server or time out.