XX：那飘过的100~_~{2014/10/03 10:57}

   UDP是一种面向非连接SOCK_DGRAM，提供无连接服务。数据包以独立包形式发送，不提供无措保证，数据可以丢失或重复。

    UDP的Server和Client的区别相对比较模糊，只要调用 sendto和 recvfrom 就可以给指定的地址收发数据。

    1. 服务器端：

// udpClient.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "tchar.h"

#pragma comment(lib,"wsock32.lib")
#include <stdio.h>
#include <winsock2.h>

BOOL InitWinsock();				//Winsock服务初始化

void main()
{

	SOCKET socket1;
	InitWinsock();
	struct sockaddr_in local;
	struct sockaddr_in from;
	int err;
	int fromlean=sizeof(from);

	local.sin_family=AF_INET;
	local.sin_port=htons(1234);					//监听端口	
	local.sin_addr.S_un.S_addr=INADDR_ANY;		//本机
	socket1=socket(AF_INET,SOCK_DGRAM,0);

	bind(socket1,(sockaddr *)&local,sizeof local);
	while(true)
	{
		char buffer[1024]="\0";
		printf("waiting for message from others \n");
		
		err=recvfrom(socket1,buffer,sizeof(buffer),0,(sockaddr *)&from,&fromlean);
		if(err!=SOCKET_ERROR)
		{

			printf("Received from %s--%s\n",inet_ntoa(from.sin_addr),buffer);
			//给Client发信息
			sendto(socket1,buffer,sizeof buffer,0,(sockaddr *)&from,fromlean);
		}
		Sleep(500);
	}
	closesocket(socket1);
}



BOOL InitWinsock()
{
	int Error;
	WORD Version;
	WSADATA Wsa;
	Version=MAKEWORD(2,2);
	Error=WSAStartup(Version,&Wsa);

	if(Error!=0)
	{
		return FALSE;
	}
	else
	{
		if(LOBYTE(Wsa.wVersion)!=2 || HIBYTE(Wsa.wHighVersion)!=2)
		{
			WSACleanup();
			return FALSE;
		}
	}
	return TRUE;
}

// udpClient.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "tchar.h"

#pragma comment(lib,"wsock32.lib")
#include <stdio.h>
#include <winsock2.h>

BOOL InitWinsock();				//Winsock服务初始化

void main()
{

	SOCKET socket1;
	InitWinsock();
	struct sockaddr_in server;
	int err;
	int lean=sizeof(server);
	server.sin_family=AF_INET;
	server.sin_port=htons(1234);								//服务器的监听端口为1234
	server.sin_addr.S_un.S_addr=inet_addr("192.168.1.18");		//设置为本机地址
	socket1=socket(AF_INET,SOCK_DGRAM,0);
	while(true)
	{
		char buffer[1024]="\0";
		printf("input message \n");
		scanf("%s",buffer);

		if(strcmp(buffer,"bye")==0)
		{
			break;
		}
		err=sendto(socket1,buffer,sizeof(buffer),0,(sockaddr *)&server,lean);
		if(err!=SOCKET_ERROR)
		{

			err=recvfrom(socket1,buffer,sizeof(buffer),0,(sockaddr *)&server,&lean);
			if(err!=SOCKET_ERROR)
			{

				printf("receive from server:%s\n",buffer);
			}
		}
	}
	closesocket(socket1);
}



BOOL InitWinsock()
{
	int Error;
	WORD Version;
	WSADATA Wsa;
	Version=MAKEWORD(2,2);
	Error=WSAStartup(Version,&Wsa);

	if(Error!=0)
	{
		return FALSE;
	}
	else
	{
		if(LOBYTE(Wsa.wVersion)!=2 || HIBYTE(Wsa.wHighVersion)!=2)
		{
			WSACleanup();
			return FALSE;
		}
	}
	return TRUE;
}

    程序仍然存在很大的问题，慢慢修改咯！

基于UDP的通讯