About multiple timeout in Socket Programming
I am implementing a peer-to-peer program: When a computer A receives “get file XXX” from stdio, it broadcasts (floods) a request packet to ask others. Both Computer B and C have the file so they send back responses. Computer A pick up B and sends confirm to B. at the same time, it creates a server socket to listen to connection. After Compute B receives the confirm from A, it creates a client socket to connects to A.
I set timeouts to both request and confirm packets. If no response is received by A after timeout, A needs to flood a new request packet again. Otherwise, A cancels timeout of the request. For the same reason, if B does not connect to A, A will send a confirm to C so that C can connect to A
My Questions: How to set timeout?
a. I can use select(). But since I already put a select() with timeout parameter as NULL in a while loop to monitor stdio, request, confirm/response packets, it seems that there is no place to put other selects with timeout parameters。
b. I can use alarm(). But there is no way to know, which request/confirm of which file the alarm() is for. And if I cancle a timeout using alarm(0), other timeout using alarm() is also canceled.
c. I also thought about using fork（）+ select(): But after the child process is terminated, how do I know it is terminated because of timeout or because response or connection is received? Besides, If it is terminated because of timout, In which part of program should I re-flood the request or re-send the confirm packet?
I want to solve the problem and need your help. Can any guru answer the question? Thanks