Linux网络编程之线程

花了点时间写了个线程版的回射服务器，下面记录代码和遇到的问题和解决的办法

/*************************************************************************
    > File Name: echo_serv.c
    > Author: gwjiaoj
    > Mail: [e-mail]
    > Created Time: Fri 27 Nov 2015 02:15:38 GMT
 ************************************************************************/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
#include <strings.h>

#define ERR_EXIT(exp) do\
    {\
        perror(exp);\
        exit(EXIT_FAILURE);\
    } while (0)

void * do_it(void *pconnfd)
{
    int recvbuf[1500] = { 0 };
    int connfd = (int)pconnfd;
    pthread_detach(pthread_self());
    printf("%d\n", connfd);
    for( ; ; )
    {
        memset(recvbuf, 0, sizeof(recvbuf));
        if(read(connfd, recvbuf, sizeof(recvbuf)) < 0)
        {
            ERR_EXIT("read");
        }

        printf("%s\n", recvbuf);

        if(write(connfd, recvbuf, strlen(recvbuf)) < 0)
        {
            ERR_EXIT("write");
        }
    }

    close(connfd);

    return;
}
int main(int argc, void **argv)
{
    pthread_t tid = 0;
    int listenfd = 0;
    int connfd = 0;
    struct sockaddr_in serveraddr = { 0 };
    struct sockaddr_in peeraddr = { 0 };
    char buff[1024] = { 0 };
    socklen_t socklen = 0;

    if((listenfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
    {
        ERR_EXIT("socket");
    }

    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(5188);
    serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);

    if(bind(listenfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0)
    {
        ERR_EXIT("bind");
    }

    if(listen(listenfd, SOMAXCONN) < 0)
    {
        ERR_EXIT("listen");
    }

    while(1)
    {
        memset(&peeraddr, 0, sizeof(peeraddr));
        socklen = sizeof(peeraddr);

        if((connfd = accept(listenfd, (struct sockaddr *)&peeraddr, &socklen)) < 0)
        {
            ERR_EXIT("accept");
        }

        inet_ntop(AF_INET, &peeraddr.sin_addr, buff, sizeof(buff));
        printf("%d\n", connfd);
        printf("ip: %s, port: %d\n", buff, peeraddr.sin_port);
        if(0 != pthread_create(&tid, NULL, do_it, (void *)connfd))
        {
            ERR_EXIT("pthread");
        }
    }

    return 0;
}

/*************************************************************************
    > File Name: echo_cli.c
    > Author: gwjiaoj
    > Mail: [e-mail]
    > Created Time: Fri 27 Nov 2015 02:15:38 GMT
 ************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
#include <strings.h>

#define ERR_EXIT(exp) do\
    {\
        perror(exp);\
        exit(EXIT_FAILURE);\
    } while (0)

int main(int argc, void **argv)
{
    int localfd = 0;
    struct sockaddr_in serveraddr = { 0 };
    struct sockaddr_in localaddr = { 0 };
    socklen_t addrlen = 0;
    char recvbuf[1024] = { 0 };
    char sendbuf[1024] = { 0 };
    char buff[1024] = { 0 };

    if(2 != argc)
    {
        printf("usage: a.out \n");
        return 0;
    }

    if((localfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)
    {
        ERR_EXIT("socket error");
    }

    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(5188);
    serveraddr.sin_addr.s_addr = inet_addr(argv[1]);
    if(connect(localfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0)
    {
        ERR_EXIT("connect error");
    }
    memset(&localaddr, 0, sizeof(localaddr));
    addrlen = sizeof(localaddr);
    if(getsockname(localfd, (struct sockaddr *)&localaddr, &addrlen) < 0)
    {
        ERR_EXIT("getsockname error");
    }

    inet_ntop(AF_INET, &localaddr.sin_addr, buff, sizeof(buff));

    printf("ip: %s, port %d\n", buff,
               ntohs(localaddr.sin_port));

    while(1)
    {
        if(fgets(sendbuf, sizeof(sendbuf), stdin) == NULL)
        {
            ERR_EXIT("fgets error");
        }

        if(write(localfd, sendbuf, strlen(sendbuf)) < 0)
        {
            ERR_EXIT("write error");
        }

        if(read(localfd, recvbuf, sizeof(recvbuf)) < 0)
        {
            ERR_EXIT("read error");
        }

        if(fputs(recvbuf, stdout) == EOF)
        {
            ERR_EXIT("fputs error");
        }
    }

    return 0;
}

在使用线程时，使用gcc或arm-linux-gcc编译时，会出现错误：undefined reference to 'pthread_create'
主要是以下两种原因：
1、#include  请确认头文件是否添加
2、-lpthread 编译选项，即在编译时需添加额外的编译选项，如使用gcc编译echo_serv.c文件，命令正确应该如下：
    gcc echo_serv.c -o echo_serv  -lpthread
    请注意后面的-lpthread，特别是-后边的'l'，link = 'l'