poll()例程（包含 bind,listen,accept,setsockopt 的用法）

Using
The
The

Socket flow of events: Server that uses 0
Indicates that the process times out. In this example, the timeout is set for 3 minutes (in milliseconds).
-1
Indicates that the process has failed.
1
Indicates only one descriptor is ready to be processed, which is processed only if it is the listening socket.
1++
Indicates that multiple descriptors are waiting to be processed. The poll() API allows simultaneous connection with all descriptors in the queue on the listening socket.
The #include<stdio.h>#include<stdlib.h>#include<sys/ioctl.h>#include<sys/poll.h>#include<sys/socket.h>#include<sys/time.h>#include<netinet/in.h>#include<errno.h>#defineSERVER_PORT12345#defineTRUE1#defineFALSE0/** * There are 2 kind of sockets, one is the only listening socket, the other is the accepted sockets. * For the listening socket, poll() returns when a connection comes; for those accepted sockets, poll() returns when * data coming form the client is readable. /intmain (int argc, char argv[]){intlen, rc, on = 1;intlisten_sd = -1, new_sd = -1;intdesc_ready, end_server = FALSE, compress_array = FALSE;intclose_conn;charbuffer[80];struct sockaddr_inaddr;inttimeout;struct pollfdfds[200];intnfds = 1, current_size = 0, i, j;/*************************************************************//* Create an AF_INET stream socket to receive incoming // connections on ///listen_sd = socket(AF_INET, SOCK_STREAM, 0);if (listen_sd < 0){perror("socket() failed");exit(-1);}/// Allow socket descriptor to be reuseable *//*************************************************************/rc = setsockopt(listen_sd, SOL_SOCKET, SO_REUSEADDR,(char *)&on, sizeof(on));if (rc < 0){perror("setsockopt() failed");close(listen_sd);exit(-1);}/*************************************************************//* Set socket to be nonblocking. All of the sockets for // the incoming connections will also be nonblocking since // they will inherit that state from the listening socket. *//*************************************************************/rc = ioctl(listen_sd, FIONBIO, (char *)&on);if (rc < 0){perror("ioctl() failed");close(listen_sd);exit(-1);}/*************************************************************//* Bind the socket *//*************************************************************/memset(&addr, 0, sizeof(addr));addr.sin_family = AF_INET;addr.sin_addr.s_addr = htonl(INADDR_ANY);addr.sin_port = htons(SERVER_PORT);rc = bind(listen_sd,(struct sockaddr *)&addr, sizeof(addr));if (rc < 0){perror("bind() failed");close(listen_sd);exit(-1);}/*************************************************************//* Set the listen back log ///rc = listen(listen_sd, 32);if (rc < 0){perror("listen() failed");close(listen_sd);exit(-1);}/// Initialize the pollfd structure ///memset(fds, 0 , sizeof(fds));/// Set up the initial listening socket ///fds[0].fd = listen_sd;fds[0].events = POLLIN;/// Initialize the timeout to 3 minutes. If no // activity after 3 minutes this program will end. // timeout value is based on milliseconds. *//*************************************************************/timeout = (3 * 60 * 1000);/*************************************************************//* Loop waiting for incoming connects or for incoming data // on any of the connected sockets. *//***/do{/// Call poll() and wait 3 minutes for it to complete. ///printf("Waiting on poll()...\n");rc = poll(fds, nfds, timeout);/// Check to see if the poll call failed. ///if (rc < 0){perror(" poll() failed");break;}/// Check to see if the 3 minute time out expired. ///if (rc == 0){printf(" poll() timed out. End program.\n");break;}/// One or more descriptors are readable. Need to // determine which ones they are. *//***/current_size = nfds;for (i = 0; i < current_size; i++){/// Loop through to find the descriptors that returned // POLLIN and determine whether it's the listening // or the active connection. ///if(fds[i].revents == 0)continue;/// If revents is not POLLIN, it's an unexpected result, // log and end the server. *//***/if(fds[i].revents != POLLIN){printf(" Error! revents = %d\n", fds[i].revents);end_server = TRUE;break;}/// Listening descriptor is readable. ///if (fds[i].fd == listen_sd){printf(" Listening socket is readable\n");/// Accept all incoming connections that are // queued up on the listening socket before we // loop back and call poll again. *//***/do{/// Accept each incoming connection. If // accept fails with EWOULDBLOCK, then we // have accepted all of them. Any other // failure on accept will cause us to end the // server. *//*****/new_sd = accept(listen_sd, NULL, NULL);if (new_sd < 0){/// If the errno is EAGAIN or EWOULDBLOCK, then // no pending connections are present on the // queue, which indicates we have accept all of // them. ///if (errno != EWOULDBLOCK){perror(" accept() failed");end_server = TRUE;}break;}/*****//* Add the new incoming connection to the // pollfd structure ///printf(" New incoming connection - %d\n", new_sd);fds[nfds].fd = new_sd;fds[nfds].events = POLLIN;nfds++;/// Loop back up and accept another incoming // connection ///} while (new_sd != -1);}/*****//* This is not the listening socket, therefore an // existing connection must be readable *//***/else{printf(" Descriptor %d is readable\n", fds[i].fd);close_conn = FALSE;/// Receive all incoming data on this socket // before we loop back and call poll again. *//***/do{/// Receive data on this connection until the // recv fails with EWOULDBLOCK. If any other // failure occurs, we will close the // connection. ///rc = recv(fds[i].fd, buffer, sizeof(buffer), 0);if (rc < 0){if (errno != EWOULDBLOCK){perror(" recv() failed");close_conn = TRUE;}break;}/// Check to see if the connection has been // closed by the client ///if (rc == 0){printf(" Connection closed\n");close_conn = TRUE;break;}/// Data was received ///len = rc;printf(" %d bytes received\n", len);/// Echo the data back to the client ///rc = send(fds[i].fd, buffer, len, 0);if (rc < 0){perror(" send() failed");close_conn = TRUE;break;}} while(TRUE);/***//* If the close_conn flag was turned on, we need // to clean up this active connection. This // clean up process includes removing the // descriptor. *//*******************************************************/if (close_conn){close(fds[i].fd);fds[i].fd = -1;compress_array = TRUE;}} /* End of existing connection is readable /} / End of loop through pollable descriptors *//***********************************************************//* If the compress_array flag was turned on, we need // to squeeze together the array and decrement the number // of file descriptors. We do not need to move back the // events and revents fields because the events will always// be POLLIN in this case, and revents is output. *//***********************************************************/if (compress_array){compress_array = FALSE;for (i = 0; i < nfds; i++){if (fds[i].fd == -1){for(j = i; j < nfds; j++){fds[j].fd = fds[j+1].fd;}nfds--;}}}} while (end_server == FALSE); /* End of serving running. *//*************************************************************//* Clean up all of the sockets that are open *//*************************************************************/for (i = 0; i < nfds; i++){if(fds[i].fd >= 0){close(fds[i].fd);}}}
参考资料：
http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/index.jsp?topic=/rzab6/poll.htm