linux c下简单实现服务端与多客户端同时连接

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参考文章：

http://blog.csdn.net/kangroger/article/details/41753605

http://www.cnblogs.com/xudong-bupt/archive/2013/12/29/3483059.html

对于服务器端来说，通过bind、listen，之后accept建立新的连接。accept返回的句柄建立的连接包括四部分：源IP、源端口号、目的IP、目的端口号。这样在一个应用程序中，就算和多个客户端建立连接，在收到数据后，应用程序通过目的IP和目的端口号也能区分是哪一条连接。

服务端：

#include <sys/types.h>#include <sys/socket.h>#include <stdio.h>#include <netinet/in.h>#include <arpa/inet.h>#include <unistd.h>#include <string.h>#include <stdlib.h>#include <fcntl.h>#include <sys/shm.h>#define PORT  8890#define QUEUE_SIZE   10#define BUFFER_SIZE 1024void str_echo(int sockfd)  {      char buffer[BUFFER_SIZE];    pid_t pid = getpid();    while(1)    {        memset(buffer,0,sizeof(buffer));        int len = recv(sockfd, buffer, sizeof(buffer),0);        if(strcmp(buffer,"exit\n")==0)        {    printf("child process: %d exited.\n",pid);            break;        }printf("pid:%d receive:\n",pid);        fputs(buffer, stdout);        send(sockfd, buffer, len, 0);    }    close(sockfd);}int main(int argc, char **argv) {    //定义IPV4的TCP连接的套接字描述符    int server_sockfd = socket(AF_INET,SOCK_STREAM, 0);    //定义sockaddr_in    struct sockaddr_in server_sockaddr;    server_sockaddr.sin_family = AF_INET;    server_sockaddr.sin_addr.s_addr = htonl(INADDR_ANY);    server_sockaddr.sin_port = htons(PORT);    //bind成功返回0，出错返回-1    if(bind(server_sockfd,(struct sockaddr *)&server_sockaddr,sizeof(server_sockaddr))==-1)    {        perror("bind");        exit(1);//1为异常退出    }    printf("bind success.\n");      //listen成功返回0，出错返回-1，允许同时帧听的连接数为QUEUE_SIZE    if(listen(server_sockfd,QUEUE_SIZE) == -1)    {        perror("listen");        exit(1);    }    printf("listen success.\n");    for(;;)    {        struct sockaddr_in client_addr;        socklen_t length = sizeof(client_addr);         //进程阻塞在accept上，成功返回非负描述字，出错返回-1        int conn = accept(server_sockfd, (struct sockaddr*)&client_addr,&length);     if(conn<0)    {            perror("connect");            exit(1);    }        printf("new client accepted.\n");                pid_t childid;        if(childid=fork()==0)//子进程        {            printf("child process: %d created.\n", getpid());            close(server_sockfd);//在子进程中关闭监听              str_echo(conn);//处理监听的连接              exit(0);        }    }    printf("closed.\n");    close(server_sockfd);    return 0;}

客户端：

#include <sys/types.h>#include <sys/socket.h>#include <stdio.h>#include <netinet/in.h>#include <arpa/inet.h>#include <unistd.h>#include <string.h>#include <stdlib.h>#include <fcntl.h>#include <sys/shm.h>#define PORT  8890#define BUFFER_SIZE 1024int main(int argc, char **argv){    if(argc!=2)      {          printf("usage: client IP \n");          exit(0);      }    //定义IPV4的TCP连接的套接字描述符    int sock_cli = socket(AF_INET,SOCK_STREAM, 0);    //定义sockaddr_in    struct sockaddr_in servaddr;    memset(&servaddr, 0, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = inet_addr(argv[1]);    servaddr.sin_port = htons(PORT);  //服务器端口     //连接服务器，成功返回0，错误返回-1    if (connect(sock_cli, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)    {        perror("connect");        exit(1);    }    printf("connect server(IP:%s).\n",argv[1]);      char sendbuf[BUFFER_SIZE];    char recvbuf[BUFFER_SIZE];    //客户端将控制台输入的信息发送给服务器端，服务器原样返回信息    while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)    {        send(sock_cli, sendbuf, strlen(sendbuf),0); ///发送        if(strcmp(sendbuf,"exit\n")==0)        {    printf("client exited.\n");            break;        }        printf("client receive:\n");        recv(sock_cli, recvbuf, sizeof(recvbuf),0); ///接收        fputs(recvbuf, stdout);        memset(sendbuf, 0, sizeof(sendbuf));        memset(recvbuf, 0, sizeof(recvbuf));    }    close(sock_cli);    return 0;}

server端起来后，端口情况如下：

client1和client2起来后，端口情况如下：

server运行情况如下：

client1运行情况如下：

client2运行情况如下：

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