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 200
int fd_A[BACKLOG];    // accepted connection fd
int conn_amount;    // current connection amount

void 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]);
        }
    }

select监听多个客户端 -- linux函数

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原文地址：http://blog.csdn.net/cy_cai/article/details/46840555