《UNIX网络编程》之点对点通信

思路：

点对点通信，其原理也比较简单，在前面回显服务器的基础上，我们分别在服务端和客户端都使用两个线程，一个线程负责发送数据包，一个线程负责接收数据包。

代码如下：

客户端：

/*************************************************************************

    > File Name: p2pcli.c

    > Author: ma6174

    > Mail: ma6174@163.com

    > Created Time: Sun 05 Oct 2014 09:26:40 PM HKT

 ************************************************************************/

#include<stdio.h>

#include <errno.h>

#include <stdlib.h>

#include <unistd.h>

#include <signal.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <string.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#define ERR_EXIT(m) \

        do \

        { \

            perror(m); \

            exit(EXIT_FAILURE); \

        }while()

void handler(int sig)

{

    printf("recv a sigal sig = %d\n", sig);

    printf("parent exit\n");

    exit();

}

int main(int argc, char **argv)

{

    int sockfd;

    struct sockaddr_in servaddr;

    if(argc != )

    {

        //printf("usage: p2pcli <IPaddress> ");

        //exit(0);

        ERR_EXIT("usage: p2pcli <IPaddress> ");

    }

    sockfd = socket(AF_INET, SOCK_STREAM, );

    memset(&servaddr, , sizeof(servaddr));

    servaddr.sin_family = AF_INET;

    servaddr.sin_port = htons();

    servaddr.sin_addr.s_addr = inet_addr(argv[]);

    if(connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < )

    {

        ERR_EXIT("connect");

    }

    pid_t pid;

    pid = fork();

    if(pid == -)

    {

        ERR_EXIT("fork");

    }

    else if(pid == )

    {

        //child

        char recvbuf[] = {};

        while()

        {

            memset(recvbuf, , sizeof(recvbuf));

            int ret = read(sockfd, recvbuf, sizeof(recvbuf));

            if(ret == -)

            {

                ERR_EXIT("read");

                break;

            }

            else if(ret == )

            {

                printf("peer client close.\n");

                break;

            }

            else

            {

                fputs(recvbuf, stdout);

            }

        }

        printf("child thread exit\n");

        kill(getppid(), SIGUSR1);

        exit(EXIT_SUCCESS);

    }

    else

    {

        signal(SIGUSR1, handler);

        char sendbuf[] = {};

        while(fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)

        {

            //send to server.

            write(sockfd, sendbuf, strlen(sendbuf));

            memset(sendbuf, , sizeof(sendbuf));

        }

        exit(EXIT_SUCCESS);

    }

    //communication

    return ;

}

服务端：

/*************************************************************************

    > File Name: p2psrv.c

    > Author: ma6174

    > Mail: ma6174@163.com

    > Created Time: Sun 05 Oct 2014 08:27:06 PM HKT

 ************************************************************************/

#include<stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <unistd.h>

#include <signal.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <sys/socket.h>

#include <string.h>

#include <arpa/inet.h>

#define ERR_EXIT(m)\

        do\

        {\

            perror(m);\

            exit(EXIT_FAILURE);\

        }while()

/**

 *child thread signal exit function

 **/

void handler(int sig)

{

    printf("recv a signal sig=%d\n", sig);

    printf("child exit\n");

    exit(EXIT_SUCCESS);

}

int main()

{

    int listenfd;

    if( (listenfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < )

    {

        ERR_EXIT("socket");

    }

    struct sockaddr_in servaddr;

    memset(&servaddr, , sizeof(servaddr));

    servaddr.sin_family = AF_INET;

    servaddr.sin_port = htons();

    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

    //reuse address

    int on = ;

    if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)))

    {

        ERR_EXIT("setsockopt");

    }

    if(bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < )

    {

        ERR_EXIT("bind");

    }

    if(listen(listenfd, SOMAXCONN) < )

    {

        ERR_EXIT("listen");

    }

    struct sockaddr_in peeraddr;

    socklen_t peerlen = sizeof(peeraddr);

    int connfd;

    if( (connfd = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen)) <  )

    {

        ERR_EXIT("accept");

    }

    printf("ip=%s, port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));

    pid_t pid;

    pid = fork();

    if(pid == -)

    {

        ERR_EXIT("fork");

    }

    else if(pid == )

    {

        //child

        signal(SIGUSR1, handler);

        char sendbuf[];

        memset(sendbuf, , sizeof(sendbuf));

        while(fgets(sendbuf, sizeof(sendbuf), stdin)  != NULL)

        {

            write(connfd, sendbuf, strlen(sendbuf));

            memset(sendbuf, , sizeof(sendbuf));

        }

        exit(EXIT_SUCCESS);

    }

    else

    {

        char recvbuf[];

        while()

        {

            memset(recvbuf, , sizeof(recvbuf));

            int ret = read(connfd, recvbuf, sizeof(recvbuf));

            if(ret == -)

            {

                ERR_EXIT("read");

            }

            else if(ret == )

            {

                printf("peer client close.\n");

                break;

            }

            else

            {

                fputs(recvbuf, stdout);

            }

        }

        printf("parent exit\n");

        kill(pid, SIGUSR1);

        exit(EXIT_SUCCESS);

    }

    close(connfd);

    close(listenfd);

    return ;

}

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