代码：

server:

#include<netinet/in.h>
#include<sys/socket.h>
#include<sys/wait.h>
#include <arpa/inet.h>
#include<unistd.h>
int main(int argc,char**argv)
{
int sockfd, new_fd;/*监听socket:sock_fd,数据传输socket:new_fd*/
struct sockaddr_in my_addr;/*本机地址信息*/
struct sockaddr_in their_addr;/*客户地址信息*/
unsigned int sin_size,myport,lisnum;if(argv[1])myport=atoi(argv[1]);
elsemyport=7838;if(argv[2])lisnum=atoi(argv[2]);elselisnum=2;if((sockfd=socket(PF_INET,SOCK_STREAM,0))==-1){
perror("socket");
exit(1);
}
my_addr.sin_family=PF_INET;
my_addr.sin_port=htons(myport);
my_addr.sin_addr.s_addr=INADDR_ANY;
bzero(&(my_addr.sin_zero),0);
if(bind(sockfd,(struct sockaddr*)&my_addr,sizeof(struct sockaddr))==-1){
perror("bind");
exit(1);
}if(listen(sockfd,lisnum)==-1){
perror("listen");
exit(1);
}
while(1){
sin_size=sizeof(struct sockaddr_in);
if((new_fd=accept(sockfd,(struct sockaddr*)&their_addr,&sin_size))==-1){
perror("accept");
continue;
}
printf("server:gotconnectionfrom%s\n",inet_ntoa(their_addr.sin_addr));
if(!fork()){/*子进程代码段*/
if(send(new_fd,"Hello,world!\n",14,0)==-1){
perror("send");
close(new_fd);
exit(0);
}
}
close(new_fd);/*父进程不再需要该socket*/
waitpid(-1,NULL,WNOHANG);/*等待子进程结束，清除子进程所占用资源*/
}
}

client:

#include<netdb.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<sys/socket.h>
#include<unistd.h>
#define MAXDATASIZE 100/*每次最大数据传输量*/
/*********************************************************************
*filename:cycletcpclient.c
*purpose:循环tcp客户端程序
*tidiedby:zhoulifa(zhoulifa@163.com)周立发(http://zhoulifa.bokee.com)
Linux爱好者Linux知识传播者SOHO族开发者最擅长C语言
*datetime:2006-07-0422:20:00
*Note:任何人可以任意复制代码并运用这些文档，当然包括你的商业用途
*但请遵循GPL
*Thanksto:Google.com
*Hope:希望越来越多的人贡献自己的力量，为科学技术发展出力
*********************************************************************/int main(int argc,char*argv[])
{
int sockfd,numbytes;
char buf[MAXDATASIZE];
struct hostent*he;
struct sockaddr_in their_addr;
unsigned int myport;if(argv[2])myport=atoi(argv[2]);
else myport=7838;if(argc!=3){
fprintf(stderr,"usage:%shostnameport\n",argv[0]);
exit(1);
}
if((he=gethostbyname(argv[1]))==NULL){
perror("gethostbyname");
exit(1);
}
if((sockfd=socket(PF_INET,SOCK_STREAM,0))==-1){
perror("socket");
exit(1);
}
their_addr.sin_family=PF_INET;
their_addr.sin_port=htons(myport);
their_addr.sin_addr=*((struct in_addr*)he->h_addr);
bzero(&(their_addr.sin_zero),0);
if(connect(sockfd,(struct sockaddr*)&their_addr,sizeof(struct sockaddr))==-1){
perror("connect");
exit(1);
}
if((numbytes=recv(sockfd,buf,MAXDATASIZE,0))==-1){
perror("recv");
exit(1);
}
buf[numbytes]=0;
printf("Received:%s\n",buf);
close(sockfd);
return 0;
}