服务器端#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<sys/stat.h>
#include<arpa/inet.h>
#include <sys/select.h>#define MAXBUF 256
#define MAXLISTEN 8
#define PORT 8888struct msgtemp 
{
int num;
char *s;
};int main()
{
int clen,dirnum,opt=1,i,nbyte;
int listenfd,clientfd,maxfd;
int client[FD_SETSIZE];struct sockaddr_in client_addr,server_addr;
char readbuf[MAXBUF],writebuf[MAXBUF];
struct msgtemp msg[FD_SETSIZE];
fd_set rset, allset;if((listenfd=socket(AF_INET,SOCK_STREAM,0))<0){
perror("socket error:");
exit(1);
}
clen = sizeof(client_addr);
bzero(&server_addr,0);
server_addr.sin_family =AF_INET;
server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
server_addr.sin_port=htons(PORT);setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,(char*)&opt,sizeof(opt)); 
if(bind(listenfd,(struct sockaddr *)&server_addr,sizeof(server_addr))<0){
perror("bind error");
exit(1);
}
if(listen(listenfd,MAXLISTEN)<0){
perror("listen error:");
exit(1);
}maxfd = listenfd;
for (i = 0; i < FD_SETSIZE; i++) 
client[i] = -1;FD_ZERO(&allset);
FD_SET(listenfd, &allset);while(1){
rset = allset;
if(select(maxfd+1, &rset, NULL, NULL, NULL)<0)
{
perror("select");
return -1;
}
if (FD_ISSET(listenfd, &rset)) { /* 是否有新的连接进来*/
clientfd=accept(listenfd,(struct sockaddr *)&client_addr,&clen);
if(clientfd < 0)
{
perror("accept");
}
printf("new connection fd = %d\n",clientfd);
FD_SET(clientfd, &allset);
maxfd = clientfd > maxfd ? clientfd : maxfd;
for (i = 0; i < FD_SETSIZE; i++)
if (client[i] < 0) {
client[i] = clientfd; 
break;
}
}
for (i = 0; i < FD_SETSIZE; i++)
{
if (FD_ISSET(client[i], &rset)) {
if ( (nbyte = read(client[i], readbuf, MAXBUF)) < 0) {
perror("read");
continue;} 
else if (nbyte ==0)	
{
close(client[i]);
FD_CLR(client[i], &allset); 
printf("connection fd = %d closed\n",client[i]);
client[i] = -1;
msg[i].num =0;
msg[i].s = NULL;}
else{
printf("recv msg from fd = %d : %s\n",client[i],readbuf);msg[i].s = readbuf;
sprintf(writebuf,"%03d : %s",msg[i].num,msg[i].s);
write(client[i], writebuf, strlen(writebuf)+1);
msg[i].num ++;
}}
}}
return 0;
}客户端#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<sys/stat.h>
#include<arpa/inet.h>
#include<fcntl.h>#define MAXBUF 256
#define PORT 8888int main()
{
int ssock;
int clen,readbytes,fd2,i;
struct sockaddr_in server_addr;
char writebuf[MAXBUF],readbuf[MAXBUF],file_path[MAXBUF];if((ssock=socket(AF_INET,SOCK_STREAM,0))<0){
perror("socket error:");
exit(1);
}
clen = sizeof(server_addr);
bzero(&server_addr,0);
server_addr.sin_family =AF_INET;
server_addr.sin_addr.s_addr=inet_addr("127.0.0.1");
server_addr.sin_port =htons(PORT);
if(connect(ssock,(struct sockaddr *)&server_addr,clen)<0){
perror("connect error:");
exit(1);
}while(1) 
{
printf("input msg:");
fgets(writebuf,MAXBUF,stdin);
if(write(ssock,writebuf,MAXBUF)<0)
{
perror("write error:");
}readbytes=read(ssock,readbuf,MAXBUF);
if( readbytes <0 )
{perror("read error:");
exit(1);
}
if( readbytes ==0 )
{
printf("connection closed \n");
break;
}printf("%s\n",readbuf);
}close(ssock);return 0;
}