/*
 * config.h 包含该tcp/ip套接字编程所需要的基本头文件，与server.c client.c位于同一目录下
*/#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>const int MAX_LINE = 2048;
const int PORT = 6000;
const int BACKLOG = 10;
const int LISTENQ = 6666;
const int MAX_CONNECT = 20;

/*
 * server.c为服务器端代码
*/#include "config.h"int main(int argc , char **argv)
{/*声明服务器地址和客户链接地址*/struct sockaddr_in servaddr , cliaddr;/*声明服务器监听套接字和客户端链接套接字*/int listenfd , connfd;pid_t childpid;/*声明缓冲区*/char buf[MAX_LINE];socklen_t clilen;/*(1) 初始化监听套接字listenfd*/if((listenfd = socket(AF_INET , SOCK_STREAM , 0)) < 0){perror("socket error");exit(1);}//if/*(2) 设置服务器sockaddr_in结构*/bzero(&servaddr , sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_addr.s_addr = htonl(INADDR_ANY); //表明可接受任意IP地址servaddr.sin_port = htons(PORT);/*(3) 绑定套接字和端口*/if(bind(listenfd , (struct sockaddr*)&servaddr , sizeof(servaddr)) < 0){perror("bind error");exit(1);}//if/*(4) 监听客户请求*/if(listen(listenfd , LISTENQ) < 0){perror("listen error");exit(1);}//if/*(5) 接受客户请求*/for( ; ; ){clilen = sizeof(cliaddr);if((connfd = accept(listenfd , (struct sockaddr *)&cliaddr , &clilen)) < 0 ){perror("accept error");exit(1);}//if//新建子进程单独处理链接if((childpid = fork()) == 0) {close(listenfd);//str_echossize_t n;char buff[MAX_LINE];while((n = read(connfd , buff , MAX_LINE)) > 0){write(connfd , buff , n);}exit(0);}//ifclose(connfd);}//for/*(6) 关闭监听套接字*/close(listenfd);
}

/*
 * client.c为客户端代码
*/#include "config.h"/*readline函数实现*/
ssize_t readline(int fd, char *vptr, size_t maxlen)
{ssize_t    n, rc;char  c, *ptr;ptr = vptr;for (n = 1; n < maxlen; n++) {if ( (rc = read(fd, &c,1)) == 1) {*ptr++ = c;if (c == '\n')break; /* newline is stored, like fgets() */} else if (rc == 0) {*ptr = 0;return(n - 1);    /* EOF, n - 1 bytes were read */} elsereturn(-1);       /* error, errno set by read() */}*ptr = 0; /* null terminate like fgets() */return(n);
}int main(int argc , char ** argv)
{/*声明套接字和链接服务器地址*/int sockfd;struct sockaddr_in servaddr;/*判断是否为合法输入*/if(argc != 2){perror("usage:tcpcli <IPaddress>");exit(1);}//if/*(1) 创建套接字*/if((sockfd = socket(AF_INET , SOCK_STREAM , 0)) == -1){perror("socket error");exit(1);}//if/*(2) 设置链接服务器地址结构*/bzero(&servaddr , sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_port = htons(PORT);if(inet_pton(AF_INET , argv[1] , &servaddr.sin_addr) < 0){printf("inet_pton error for %s\n",argv[1]);exit(1);}//if/*(3) 发送链接服务器请求*/if( connect(sockfd , (struct sockaddr *)&servaddr , sizeof(servaddr)) < 0){perror("connect error");exit(1);}//if/*(4) 消息处理*/char sendline[MAX_LINE] , recvline[MAX_LINE];while(fgets(sendline , MAX_LINE , stdin) != NULL)   {write(sockfd , sendline , strlen(sendline));if(readline(sockfd , recvline , MAX_LINE) == 0){perror("server terminated prematurely");exit(1);}//ifif(fputs(recvline , stdout) == EOF){perror("fputs error");exit(1);}//if}//while/*(5) 关闭套接字*/close(sockfd);
}

ALL:gcc server.c -o server -lmgcc client.c -o client -lm

$ ./server &
$ ./client 127.0.0.1
this is a test
this is a test