socket编程 —— 非阻塞socket

    在上一篇文章 《socket编程——一个简单的例子》 http://blog.youkuaiyun.com/wind19/archive/2011/01/21/6156339.aspx 中写了一个简单的tcp socket通信程序，可以进行数据的交互，但有一个问题是这个程序是阻塞的，任何socket函数都要等返回后才能进行下一步动作，如果recv一直没有数据，那么就一直不会返回，整个进程就阻塞在那。所以我们要进行改造一下，让程序不再阻塞在那，而是在有数据到来的时候读一下数据，有数据要写的时候发送一下数据。

 

    设置阻塞模式的函数一般由两个fcntl 和 ioctl

 

先放源程序，服务器端还是阻塞的，客服端改成非阻塞的，只是作为一个例子

/*server.c*/ #include <stdio.h> #include <string.h> #include <sys/socket.h> #include <netinet/in.h> #include <stdlib.h> #include <syslog.h> #include <errno.h> #define MAX_LISTEN_NUM 5 #define SEND_BUF_SIZE 100 #define RECV_BUF_SIZE 100 #define LISTEN_PORT 1010 int main() { int listen_sock = 0; int app_sock = 0; struct sockaddr_in hostaddr; struct sockaddr_in clientaddr; int socklen = sizeof(clientaddr); char sendbuf[SEND_BUF_SIZE] = {0}; char recvbuf[RECV_BUF_SIZE] = {0}; int sendlen = 0; int recvlen = 0; int retlen = 0; int leftlen = 0; char *ptr = NULL; int flags = 1; int flaglen = sizeof(flags); memset((void *)&hostaddr, 0, sizeof(hostaddr)); memset((void *)&clientaddr, 0, sizeof(clientaddr)); hostaddr.sin_family = AF_INET; hostaddr.sin_port = htons(LISTEN_PORT); hostaddr.sin_addr.s_addr = htonl(INADDR_ANY); listen_sock = socket(AF_INET, SOCK_STREAM, 0); if(listen_sock < 0) { syslog(LOG_ERR, "%s:%d, create socket failed", __FILE__, __LINE__); exit(1); } if(setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, &flags, flaglen) < 0) { syslog(LOG_ERR, "%s:%d, create socket failed", __FILE__, __LINE__); exit(1); } if(bind(listen_sock, (struct sockaddr *)&hostaddr, sizeof(hostaddr)) < 0) { syslog(LOG_ERR, "%s:%d, bind socket failed", __FILE__, __LINE__); exit(1); } if(listen(listen_sock, MAX_LISTEN_NUM) < 0) { syslog(LOG_ERR, "%s:%d, listen failed", __FILE__, __LINE__); exit(1); } while(1) { app_sock = accept(listen_sock, (struct sockaddr *)&clientaddr, &socklen); if(app_sock < 0) { syslog(LOG_ERR, "%s:%d, accept failed", __FILE__, __LINE__); exit(1); } sprintf(sendbuf, "welcome %s:%d here!/n", inet_ntoa(clientaddr.sin_addr.s_addr), clientaddr.sin_port); //send data sendlen = strlen(sendbuf) +1; retlen = 0; leftlen = sendlen; ptr = sendbuf; //while(leftlen) { syslog(LOG_ERR, "%s:%d, before send", __FILE__, __LINE__); retlen = send(app_sock, ptr, sendlen, 0); if(retlen < 0) { if(errno == EINTR) retlen = 0; else exit(1); } leftlen -= retlen; ptr += retlen; syslog(LOG_ERR, "%s:%d, after send, retlen = %d", __FILE__, __LINE__, retlen); } //receive data recvlen = 0; retlen = 0; ptr = recvbuf; leftlen = RECV_BUF_SIZE -1; //do { retlen = recv(app_sock, ptr, leftlen, 0) ; if(retlen < 0) { if(errno == EINTR) retlen = 0; else exit(1); } recvlen += retlen; leftlen -= retlen; ptr += retlen; } //while(recvlen && leftlen); printf("receive data is : %s", recvbuf); close(app_sock); } close(listen_sock); return 0; }

 

/*clent.c*/ #include <stdio.h> #include <string.h> #include <sys/socket.h> #include <netinet/in.h> #include <syslog.h> #include <errno.h> #include <stdlib.h> #include <fcntl.h> #include <stdbool.h> #include <sys/select.h> #include <sys/times.h> #define MAX_LISTEN_NUM 5 #define SEND_BUF_SIZE 100 #define RECV_BUF_SIZE 100 #define SERVER_PORT 1010 #define MAX_CONNECT_TIMES 5 bool Connect(int sock_fd, struct sockaddr* pser_addr, int* paddrlen) { if(connect(sock_fd, pser_addr, *paddrlen) < 0) { if(errno == EISCONN) { syslog(LOG_ERR, "%s:%d, connect socket completed", __FILE__, __LINE__); return true; } if(errno != EINPROGRESS && errno != EALREADY && errno != EWOULDBLOCK) { syslog(LOG_ERR, "%s:%d, connect socket failed", __FILE__, __LINE__); return false; } else { syslog(LOG_ERR, "%s:%d, connect socket does not completed", __FILE__, __LINE__); } } else { syslog(LOG_ERR, "%s:%d, connect socket completed", __FILE__, __LINE__); return true; } fd_set fds_red, fds_write; struct timeval tval; int selret = 0; tval.tv_sec = 3; tval.tv_usec = 0; int ntrytimes = 0; while(1 && ntrytimes < MAX_CONNECT_TIMES) { FD_ZERO(&fds_red); FD_SET(sock_fd, &fds_red); FD_ZERO(&fds_write); FD_SET(sock_fd, &fds_write); syslog(LOG_ERR, "%s:%d, before select", __FILE__, __LINE__); selret = select(sock_fd + 1, &fds_red, &fds_write, NULL, &tval); syslog(LOG_ERR, "%s:%d, after select", __FILE__, __LINE__); if(selret < 0) { if(errno == EINTR) { ntrytimes++; continue; } else { syslog(LOG_ERR, "%s:%d, select failed", __FILE__, __LINE__); return false; } } else if(selret == 0) { syslog(LOG_ERR, "%s:%d, connect socket timeout", __FILE__, __LINE__); ntrytimes++; continue; } else { syslog(LOG_ERR, "%s:%d, select default", __FILE__, __LINE__); if(FD_ISSET(sock_fd, &fds_red) || FD_ISSET(sock_fd, &fds_write)) { int error = 0; int len = sizeof(error); int rc = getsockopt(sock_fd, SOL_SOCKET, SO_ERROR, (void *) &error, &len); if(rc == -1) { syslog(LOG_ERR, "%s:%d, connection is closed", __FILE__, __LINE__); return false; } else if(error) { syslog(LOG_ERR, "%s:%d, connection is closed", __FILE__, __LINE__); return false; } else {