select监听多个客户端 -- linux函数
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使用select函数可以以非阻塞的方式和多个socket通信。程序只是演示select函数的使用，功能非常简单，即使某个连接关闭以后也不会修改当前连接数，连接数达到最大值后会终止程序。
1. 程序使用了一个数组fd_A，通信开始后把需要通信的多个socket描述符都放入此数组。
2. 首先生成一个叫sock_fd的socket描述符，用于监听端口。
3. 将sock_fd和数组fd_A中不为0的描述符放入select将检查的集合fdsr。
4. 处理fdsr中可以接收数据的连接。如果是sock_fd，表明有新连接加入，将新加入连接的socket描述符放置到fd_A。
这部分代码实现逻辑不错，不过有点bug，对套接字缓存未做处理完整。
#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <string.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#define MYPORT 1234 // the port users will be connecting to#define BACKLOG 5 // how many pending connections queue will hold#define BUF_SIZE 200int fd_A[BACKLOG]; // accepted connection fdint conn_amount; // current connection amountvoid showclient(){ int i; printf("client amount: %d\n", conn_amount); for (i = 0; i < BACKLOG; i++) { printf("[%d]:%d ", i, fd_A[i]); } printf("\n\n");}int main(void){ int sock_fd, new_fd; // listen on sock_fd, new connection on new_fd struct sockaddr_in server_addr; // server address information struct sockaddr_in client_addr; // connector's address information socklen_t sin_size; int yes = 1; char buf[BUF_SIZE]; int ret; int i; if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) { perror("socket"); exit(1); } if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) { perror("setsockopt"); exit(1); } server_addr.sin_family = AF_INET; // host byte order server_addr.sin_port = htons(MYPORT); // short, network byte order server_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero)); if (bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) { perror("bind"); exit(1); } if (listen(sock_fd, BACKLOG) == -1) { perror("listen"); exit(1); } printf("listen port %d\n", MYPORT); fd_set fdsr; int maxsock; struct timeval tv; conn_amount = 0; sin_size = sizeof(client_addr); maxsock = sock_fd; while (1) { // initialize file descriptor set FD_ZERO(&fdsr); FD_SET(sock_fd, &fdsr); // timeout setting tv.tv_sec = 30; tv.tv_usec = 0; // add active connection to fd set for (i = 0; i < BACKLOG; i++) { if (fd_A[i] != 0) { FD_SET(fd_A[i], &fdsr); } } ret = select(maxsock + 1, &fdsr, NULL, NULL, &tv); if (ret < 0) { perror("select"); break; } else if (ret == 0) { printf("timeout\n"); continue; } // check every fd in the set for (i = 0; i < conn_amount; i++) { if (FD_ISSET(fd_A[i], &fdsr)) { ret = recv(fd_A[i], buf, sizeof(buf), 0); if (ret <= 0) { // client close printf("client[%d] close\n", i); close(fd_A[i]); FD_CLR(fd_A[i], &fdsr); fd_A[i] = 0; } else { // receive data if (ret < BUF_SIZE) memset(&buf[ret], '\0', 1); printf("client[%d] send:%s\n", i, buf); } } } // check whether a new connection comes if (FD_ISSET(sock_fd, &fdsr)) { new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &sin_size); if (new_fd <= 0) { perror("accept"); continue; } // add to fd queue if (conn_amount < BACKLOG) { fd_A[conn_amount++] = new_fd; printf("new connection client[%d] %s:%d\n", conn_amount, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port)); if (new_fd > maxsock) maxsock = new_fd; } else { printf("max connections arrive, exit\n"); send(new_fd, "bye", 4, 0); close(new_fd); break; } } showclient(); } // close other connections for (i = 0; i < BACKLOG; i++) { if (fd_A[i] != 0) { close(fd_A[i]); } } exit(0);} for(i=0;i<BACKLOG;i++) { tcpSockIndex[i] = -1; } while(1){FD_ZERO(&readfds);FD_SET(tcpSock, &readfds); maxfdp = maxfdp>tcpSock?maxfdp:tcpSock; for(i=0;i<BACKLOG;i++) {// AB_LOG("FD_SET tcpSockIndex[%d] = %d.\n", i, tcpSockIndex[i]); if(-1 != tcpSockIndex[i]) { FD_SET(tcpSockIndex[i], &readfds); maxfdp = maxfdp>tcpSockIndex[i]?maxfdp:tcpSockIndex[i]; } } timeout.tv_sec = SELECT_TIME_OUT_TM; timeout.tv_usec = 0; ret = select(maxfdp+1, &readfds, NULL, NULL, &timeout);if(ret < 0){AB_PERROR("select error!\n");return ;} else if(0 == ret) {AB_PERROR("select time out!\n"); } //处理客户端发送的报文 for(i=0; i<BACKLOG; i++) { if ( -1 != tcpSockIndex[i] && FD_ISSET(tcpSockIndex[i], &readfds)) { AB_LOG("--- tcp client ---.\n"); pthread_t pthd2; TCP_SOCK_T * pTcpSock = NULL; pTcpSock = (TCP_SOCK_T *)malloc(sizeof(TCP_SOCK_T)); pTcpSock->sock = tcpSockIndex[i]; pthread_create(&pthd2, NULL, bc_sock_handle_client_data, (void *)pTcpSock); #if 0 bc_sock_handle_client_data(tcpSockIndex[i]); ret = read(tcpSockIndex[i], NULL, 0); AB_LOG("close tcpSockIndex[%d] = %d, ret = %d.\n", i, tcpSockIndex[i], ret ); //关闭客户端连接的套接字 if(-1 == tcpSockIndex[i]) close(tcpSockIndex[i]); #endif //清空客户端字符集 FD_CLR(tcpSockIndex[i], &readfds); tcpSockIndex[i] = -1; tcpClientConnNum --; } } //获取客户端连接过来的套接字 if(FD_ISSET(tcpSock, &readfds)) { AB_LOG("--- tcp server ---.\n"); if((tcpSockClient = accept(tcpSock, (struct sockaddr*)&chiAddr, &cliLen)) <= 0 ) { AB_PERROR("BCHV accept socket error: %s(errno: %d).\n",strerror(errno), errno); continue; } //在套接字数组中找出一个可用添加的位置。 for(i=0,tcpSockFlag=0; i<BACKLOG; i++) { AB_LOG("tcpSockIndex[%d] = %d.\n", i, tcpSockIndex[i]); if(-1 == tcpSockIndex[i]) { tcpSockIndex[i] = tcpSockClient; tcpClientConnNum ++; AB_LOG("new connection client[%d] %08X:%d.\n", tcpClientConnNum, chiAddr.sin_addr.s_addr, ntohs(chiAddr.sin_port)); //错误打印 //AB_LOG("new connection client[%d] %s.\n", tcpClientConnNum, // inet_ntoa(chiAddr.sin_addr)); #if 0 if (sock_c > maxfdp) maxfdp = sock_c; #endif tcpSockFlag = 1; break; } } //超过最大连接请求，可以发送客户端断开连接 if(0 == tcpSockFlag) { AB_LOG("max connections arrive, exit\n"); send(tcpSockClient, "bye", 4, 0); close(tcpSockClient); } } } //关闭所有客户端套接字 for(i=0; i<BACKLOG; i++) { if(-1 != tcpSockIndex[i]) { close(tcpSockIndex[i]); } }文章摘自 http://www.cnblogs.com/faraway/archive/2009/03/06/1404449.html
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