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POC: Data forwarding server using epoll ET fills the send buffer
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  1. POC: Data forwarding server using epoll ET fills the send buffer
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    copied!<p>I have the following situation. My server receives data from remote server (fd_server) and forwards it to the client (fd_client). I'm using edge triggered epoll so I can handle multiple clients and multiple server conncetions.</p> <p>Procedure:</p> <ol> <li>client connects to the server.</li> <li>my server connects to the remote server and requests data.</li> <li>remote server responds and my server forwards data to the client.</li> </ol> <p>Details:</p> <p>After my server connects to the remote server the fd_server is added to epoll control with EPOLLIN flag. Server waits for events.</p> <p>When epoll_wait return the fd_server as readable I go in the following loop displayed bellow.</p> <p>After some read/writes my sctp_sendmsg return EAGAIN, which means sctp send buffer is full. How should I handle this situation without loosing the data I have already read from the fd_server socket?</p> <p>IS there a way of knowing before hand, how much data can I send, so I only read the right amount?</p> <pre><code>while(1){ N = recv(fd_server,buf, sizeof buf,0); if (N == -1){ /* If errno == EAGAIN, that means we have read all data. So go back to the main loop. */ if (errno != EAGAIN){ perror ("tcp_recv error"); } break; } if(N == 0){ /* End of file. The remote has closed the connection. */ close(fd_server); break; } pos = 0; while(pos &lt; N){ got = sctp_sendmsg(fd_client, &amp;buf[pos], N-pos, to, tolen, 0, 0, stream, 0, 0); if(got&lt;=0){ if (errno == EAGAIN){ //what to do? }else{ perror("tcp to sctp send error"); } } else{ pos += got;} } } </code></pre>
 

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