Linux C局域网通信程序刘志卿

作者：2009级嵌入式刘志卿

这是一个局域网通信程序,客户端通过连接服务器向局域网中的其它主机进行通讯.
/*
-------------------------------------------------------------------------------------
服务器程序,用下面的命令直接编译,运行.
[root@localhost liu]# gcc server.c -o server
-------------------------------------------------------------------------------------*/
                            /*server.c*/
#include
#include
#include
#include
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char **argv)
{
    int i, maxi, maxfd, listenfd, connfd, sockfd;
    int nready, client[FD_SETSIZE];
    ssize_t n;
    fd_set rset, allset;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    socklen_t cliaddr_len;
    struct sockaddr_in cliaddr, servaddr;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

    Listen(listenfd, 20);

    maxfd = listenfd;    /* initialize */
    maxi = -1;        /* index into client[] array */
    for (i = 0; i < FD_SETSIZE; i++)
        client[i] = -1;    /* -1 indicates available entry */
    FD_ZERO(&allset);
    FD_SET(listenfd, &allset);

    for (;;) {
        rset = allset;    /* structure assignment */
        nready = select(maxfd + 1, &rset, NULL, NULL, NULL);
        if (nready < 0)
            perr_exit("select error");

        if (FD_ISSET(listenfd, &rset)) {    /* new client connection */
            cliaddr_len = sizeof(cliaddr);
            connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);

            printf("received from %s at PORT %d ", inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)), ntohs(cliaddr.sin_port));

            for (i = 0; i < FD_SETSIZE; i++)
                if (client[i] < 0) {
                    client[i] = connfd;    /* save descriptor */
                    break;
                }
            if (i == FD_SETSIZE) {
                fputs("too many clients ", stderr);
                exit(1);
            }

            FD_SET(connfd, &allset);    /* add new descriptor to set */
            if (connfd > maxfd)
                maxfd = connfd;    /* for select */
            if (i > maxi)
                maxi = i;    /* max index in client[] array */

            if (--nready == 0)
                continue;    /* no more readable descriptors */
        }

        for (i = 0; i <= maxi; i++) {    /* check all clients for data */
            if ((sockfd = client[i]) < 0)
                continue;
            if (FD_ISSET(sockfd, &rset)) {
                if ((n = Read(sockfd, buf, MAXLINE)) < 0) {    //读取客户端发送的内容
                    /*connection closed by client */
                    Close(sockfd);                               //如果读取失败则关闭连接
                    FD_CLR(sockfd, &allset);                   //把这个文件描述符从连接中清除
                    client[i] = -1;                            //把客户端标志设为-1
                } else {

                    int j;
                    for (j = 0; j <= maxi; j++) {
                        if (FD_ISSET(sockfd, &rset))
                            Write(client[j], buf, n);            //把已读到的数据发送给每一个连接的客户端

                    }

                }

                if (--nready == 0)
                    break;    /* no more readable descriptors */
            }
        }
    }
}
/*------------------------------------------------------------------------------------
执行过程如下：
[root@localhost liu]# ./server
received from 127.0.0.1 at PORT 33679                   //客户端连接上服务器
received from 127.0.0.1 at PORT 33680
-------------------------------------------------------------------------------------*/

/*-------------------------------------------------------------------------------------------
注释：程序编译后直接运行,为了可以看到结果,可以打开多个终端进行测试,也可以在局域网内,两台以上的电脑进行测试.如果是局域网内多台电脑测试,则需要服务器端打开8000

端口.用下面的命令编译程序.
[root@localhost liu]# gcc client.c -o client
--------------------------------------------------------------------------------------------*/

                            /* client.c */
#include
#include
#include
#include
#include "wrap.h"
#include
#include
#include

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char *argv[])
{
    struct sockaddr_in servaddr;
    char buf[MAXLINE];
    int sockfd, n;
    pid_t pid;

    sockfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);

    Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

    pid = fork();                                       //分支为两个进程

    if (pid > 0) {        //父进程
        while (fgets(buf, MAXLINE, stdin) != NULL) {
            Write(sockfd, buf, strlen(buf));              //向客户端发送数据
        }
    }
    if (pid == 0) {        //子进程
        int b_on = 1;
        ioctl(sockfd, FIONBIO, &b_on);
        for (;;)
            if ((n = Read(sockfd, buf, MAXLINE)) > 0)    //向服务器接收数据
                Write(STDOUT_FILENO, buf, n);              //把读到的数据写进标准输出
    }
    Close(sockfd);
    return 0;
}

/*------------------------------------------------------------------------------------
执行过程如下：
[root@localhost liu]# ./client
ni hao a                                            //客户端向服务器发送数据
ni hao a                                            //服务器端接收数据后发送给每一个已连接的客户端
hello
hello
hello!
hello!

-------------------------------------------------------------------------------------*/

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Linux C局域网通信程序 刘志卿

Linux C局域网通信程序刘志卿