程序代码：

#include<sys/socket.h>
#include<errno.h>
#include<netinet/in.h>
#include<unistd.h>
#include<stdio.h>
#include<sys/wait.h>
#include<signal.h>
#include<string.h>

#define MAXLEN 1000

void sig_cld(int sig) 
{
    pid_t pid;
    while(  (pid = waitpid(-1, NULL, WNOHANG) )> 0)
        printf("process %d has exited\n", pid);
}


int main(int argc, char **argv)
{
    int listenfd;
    if ( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        fputs("socket failed", stderr);
    struct sockaddr_in servaddr;
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(6014);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    bind(listenfd,(struct sockaddr *) &servaddr, sizeof(servaddr));
    listen(listenfd, 11);
    signal(SIGCHLD, sig_cld);
    while(1) {
        int connfd;
        char recvbuff[MAXLEN], sendbuff[MAXLEN];
        if( (connfd = accept(listenfd, NULL, NULL)) < 0){
            if(errno == EINTR) continue;
                        else fputs("accept Error", stderr);
        }
        pid_t pid;
        if( (pid = fork() )== 0){
            close(listenfd);
            while(read(connfd, recvbuff, MAXLEN) > 0){
                int a,b;
                sscanf(recvbuff, "%d%d", &a, &b);
                sprintf(sendbuff, "%d", a+b);
                if( write(connfd, sendbuff, strlen(sendbuff)) < 0)
                    fputs("Write Error", stderr);
            }
            return 0;  //为什么去掉这行 当关掉客户端时 电脑就会卡死啊？ 谁做到么
        }
        close(connfd);
    }
    return 0;
}

程序代码：

#include<netinet/in.h>
#include<sys/socket.h>
#include<stdio.h>
#include<string.h>

#define MAXLEN 1000
int main(int argc, char *argv[])
{
    if(argc != 2) fputs("Input Error", stderr);
    int sockfd[10], i;
    struct sockaddr_in clientaddr;
    for( i=0; i<10; ++i){
        if((sockfd[i] = socket(AF_INET, SOCK_STREAM, 0)) < 0)
            fputs("socket failed", stderr);
            bzero(&clientaddr,sizeof(clientaddr));
            clientaddr.sin_family = AF_INET;
            clientaddr.sin_port = htons(6014);
            if( inet_pton(AF_INET, argv[1], &clientaddr.sin_addr) <= 0)
                fputs("inet_pton Error", stderr);
        if(connect(sockfd[i], (struct sockaddr *)&clientaddr, sizeof(clientaddr)) < 0)
            fputs("Connect error", stderr);
    }
        

    char recv[MAXLEN],sendbuff[MAXLEN];
    while( fgets(sendbuff, MAXLEN, stdin)  ){
        if(write(sockfd[1], sendbuff, strlen(sendbuff)) < 0)
            fputs("write Error", stderr);
        if( read(sockfd[1], recv, MAXLEN) > 0 ){
            fputs(recv, stdout);
            fputs("\n", stdout);
        }
    }
    
    return 0;
}