server

#include <stdio.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>

void
 
 handler(int sig)
{
        printf("recv a sig=%d\n",sig);
        exit(1);
}


int main(void)
{
        int listenfd;
        listenfd = socket(PF_INET,SOCK_STREAM,0);
        if(listenfd < 0)
        {
                printf("creat socket failed\n");
                exit(1);
        }
        struct
 
 sockaddr_in servaddr;
        memset(&servaddr,0,sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(5188);
        servaddr.sin_addr.s_addr = htonl(INADDR_ANY);//host any address

        int n=1;
        if(setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&n,sizeof
 
(n))<0)
        {
                printf("set resueaddr failed\n");
                exit(1);
         }

        if(bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)
        {
                printf("bind fialed\n");
                exit(1);
        }
        if(listen(listenfd,SOMAXCONN)<0)
        {
                printf("listen failed\n");
                exit(1);
        }
        struct sockaddr_in peeraddr;
        socklen_t peerlen = sizeof(peeraddr);
        int conn;
        if((conn=accept(listenfd,(struct sockaddr*)&peeraddr,&peerlen))<0)
        {
                printf("accept failed\n");
                exit(1);
        }
        printf("ip=%s, port=%d\n",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));

        pid_t pid;
        pid = fork();
        if (pid == -1)
        {
                printf("server fork failed\n");
                exit(1);
        }

        if(pid == 0) //send to client data
        {
                char recvbuf[1024];
                while (1)
                {
                        memset(recvbuf,0 ,sizeof(recvbuf));
                        int ret = read(conn,recvbuf,sizeof(recvbuf));
                        if( ret == -1)
                        {
                                printf("server read failed\n");
                                exit(1);
                        }
                        else if (ret == 0)
                        {
                                printf("client close\n");
                                break;
                        }
                        fputs(recvbuf,stdout);
                }
                printf("parent close \n");
                kill(pid,SIGUSR1);
                close(conn);
                exit(1);
        }
        else //recv from client data
        {
                signal(SIGUSR1,handler);
                char sendbuf[1024]={0};
                while(fgets(sendbuf,sizeof(sendbuf),stdin) != NULL)
                {
                        write(conn,sendbuf,strlen(sendbuf));
                        memset(sendbuf, 0 ,sizeof(sendbuf));
                }
                printf("server childpid close\n");
                close(conn);
                exit(1);
        }
        close(listenfd);
        return 0;
}

client

#include <stdio.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>

void handler(int sig)
{
        printf("recv a sig=%d\n",sig);
        exit(1);
}

int main(void)
{
        int sock;
        sock = socket(PF_INET,SOCK_STREAM,0);
        if(sock < 0)
        {
                printf("creat socket failed\n");
                exit(1);
        }
        struct sockaddr_in servaddr;
        memset(&servaddr,0,sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(5188);
        //servaddr.sin_addr.s_addr = htonl(INADDR_ANY);//host any address
        servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");

        if(connect(sock,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)
        {
                printf("connect failed \n");
                exit(1);
        }
        pid_t pid;
        pid=fork();
        if(pid == -1)
        {
                printf("client fork failed\n");
                exit(1);
        }
        if(pid == 0) // recv from server data
        {
                char recvbuf[1024] = {0};
                while(1)
                {
                        memset(recvbuf,0,sizeof(recvbuf));
                        int ret = read(sock,recvbuf,sizeof(recvbuf));
                        if(ret == -1)
                        {
                                printf("read faileed\n");
                                exit(1);
                        }
                        else if(ret ==0)
                        {
                                printf("server close\n");
                                break;
                        }
                        fputs(recvbuf,stdout);
                }
                close(sock);
                kill(getppid(),SIGUSR1);
        }
        else //send to server data
        {
                signal(SIGUSR1,handler);
                char sendbuf[1024] = {0};
                while(fgets(sendbuf,sizeof(sendbuf),stdin) != NULL)
                {
                        write(sock, sendbuf,strlen(sendbuf));
                        memset(sendbuf,0,sizeof(sendbuf));
                }
                close(sock);
        }
        return 0;
}

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