首先看一下程序代码：
/* server.c */
#include <stdio.h>
#include <winsock2.h> /* for socket */
#include <time.h> /* for clock(); */
#define LISTEN_PORT 5500 /* listening port */
#pragma comment(lib, "ws2_32.lib") /* import library for socket */
int main()
{
HOSTENT *host_entry;
char host_name[256];
int n;
struct WSAData wsadata;
int sock, length;
struct sockaddr_in srvaddr;
struct sockaddr tcpaddr;
int msgsock;
char buf[1024];
int rval, len;
char c;
char data[1024];
int i;
clock_t t_start = clock();
if ( WSAStartup(0x0101, &wsadata) == 0) /* Initialize */
{
n = gethostname(host_name, 256); /* get localhost name */
host_entry = gethostbyname(host_name); /* get localhost address */
if ( host_entry != NULL ) /* print localhost address */
{
printf("%d.%d.%d.%d\n",
host_entry->h_addr_list[0][0]&0x00ff,
host_entry->h_addr_list[0][1]&0x00ff,
host_entry->h_addr_list[0][2]&0x00ff,
host_entry->h_addr_list[0][3]&0x00ff);
}
printf("Establish connecting & listening....\n");
sock = socket(AF_INET, SOCK_STREAM, 0); /* create socket */
if (sock < 0 )
{
printf("open socket error\n");
exit(1);
}
memset(&srvaddr, 0, sizeof(struct sockaddr) );
srvaddr.sin_family = AF_INET;
srvaddr.sin_port = htons(LISTEN_PORT);
if ( bind(sock, (struct sockaddr*)&srvaddr, sizeof(srvaddr)) < 0 ) /* bind address */
{
printf("socket bind error.\n");
exit(1);
}
length = sizeof(srvaddr);
if ( getsockname(sock, (struct sockaddr*)&srvaddr, &length ) < 0 )
{
printf("get sock name error.\n");
exit(1);
}
printf("listening port: #%d\n", ntohs(srvaddr.sin_port));
listen(sock, 5); /* listening */
len = sizeof(struct sockaddr);
do {
msgsock = accept(sock, (struct sockaddr*)&tcpaddr, (int*)&len); /* create accept sock */
if ( msgsock == -1 )
{
printf("error accept.\n");
}
else
do {
if ( clock() - t_start > 20000 )
{
closesocket(msgsock);
WSACleanup();
printf("time out.\n");
exit(0);
}
memset(buf, 0, sizeof(buf));
if (( rval = recv(msgsock, buf, 1024, 0)) < 0 ) /* receive msg */
{
printf("recv sock msg error.\n");
}
if ( rval == 0 )
{
printf("ending connecting.\n");
closesocket(msgsock);
WSACleanup();
exit(1);
}
else
{
t_start = clock();
printf("--->%s\n", buf);
}
memset(data, 0, 1024);
i = 0;
c = getchar();
while ( c != 10 )
{
data[i++] = c;
c = getchar();
}
data[i] = '\0';
send(msgsock, data, sizeof(data), 0); /* send msg */
t_start = clock();
if ( strcmp(buf, "bye") == 0 ) /* if send "bye" then end session */
{
closesocket(msgsock);
WSACleanup();
exit(1);
}
} while(rval != 0);
closesocket(msgsock);
} while(1);
}
WSACleanup();
return 0;
}
/* client.c */
#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib, "ws2_32.lib")
int main(int argc, char* argv[])
{
HOSTENT *host_entry;
char host_name[256];
int n;
struct WSAData wsadata;
int sock;
struct sockaddr_in srvaddr;
struct hostent *hp;
char data[1024];
char c;
int i = 0;
if ( argc < 3 )
{
printf("Usage : %s ip port\n", argv[0]);
exit(1);
}
if ( WSAStartup(0x0101, &wsadata) == 0)
{
n = gethostname(host_name, 256);
host_entry = gethostbyname(host_name);
if ( host_entry != NULL )
{
printf("%d.%d.%d.%d\n",
host_entry->h_addr_list[0][0]&0x00ff,
host_entry->h_addr_list[0][1]&0x00ff,
host_entry->h_addr_list[0][2]&0x00ff,
host_entry->h_addr_list[0][3]&0x00ff);
}
sock = socket(AF_INET, SOCK_STREAM, 0);
if ( sock < 0 )
{
printf("socket create error.\n");
exit(1);
}
srvaddr.sin_family = AF_INET;
hp = gethostbyname(argv[1]);
if ( hp == 0 )
{
printf("unknow host : %s\n", argv[1]);
exit(1);
}
memcpy((char*)&srvaddr.sin_addr, (char*)hp->h_addr, hp->h_length);
srvaddr.sin_port = htons((unsigned short)atoi(argv[2]));
if ( connect(sock, (struct sockaddr*)&srvaddr, sizeof(srvaddr)) < 0 ) /* connect server */
{
printf("connect server error.\n");
exit(1);
}
while ( 1 )
{
memset(data, 0, 1024);
i = 0;
c = getchar();
while ( c != 10 )
{
data[i++] = c;
c = getchar();
}
data[i] = '\0';
if ( send(sock, data, sizeof(data), 0) < 0 ) /* send msg to server */
{
printf("send data error.\n");
exit(1);
}
if (recv(sock, data, 1024, 0) ) /* receive msg from server */
{
printf("----->%s\n", data);
}
if ( strcmp(data, "bye") == 0 )
{
closesocket(sock);
printf("connecting close.\n");
WSACleanup();
exit(0);
}
}
}
WSACleanup();
return 0;
}
上面的程序在VC++6.0下编译通过。启动命令行，首先启动服务器server.exe，在端口5500监听，客户端以 client.exe ip 5500 （ip为服务器的ip地址）启动后，可以向服务器端发信息，然后服务器端收到信息后显示出来，并且向客户端回送信息，服务器端也可以自己发送信息，客户端 收到后也回送信息。上面的程序很简单，只是一个演示的程序，客户端首先发信息，然后服务器端发，然后客户端发.....，它们都不能连续发信息。当服务器 端连续20秒没有发信息或收到信息，会自动断开socket连接。有兴趣的朋友可以将它完善一下，让双方都可以自由的发送信息和接收信息。