linux c下简单实现服务端与多客户端同时连接_linux c下简单实现服务端与多客户端同时链接-优快云博客

参考文章：

http://blog.youkuaiyun.com/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 1024  
  
void 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 1024  
  
int 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：