udp客户端与服务端之间的通信实例

        为了让你更好地理解下面的程序，请先吃透tcp通信，然后来看下面的udp通信。下面，我们假设服务器的IP地址为：w.x.y.z, 那么，udp客户端与服务端的通信实例如下：

        服务端程序为：

#include 
#include 
#pragma comment(lib, "ws2_32.lib")   

int main()
{
	WORD wVersionRequested;
	WSADATA wsaData;
	
	wVersionRequested = MAKEWORD(1, 1);
	
	WSAStartup(wVersionRequested, &wsaData);

	unsigned int sockSrv = socket(AF_INET, SOCK_DGRAM, 0);

	SOCKADDR_IN addrSrv;
	addrSrv.sin_addr.S_un.S_addr = inet_addr("w.x.y.z"); // 请将w.x.y.z改为实际IP
	addrSrv.sin_family = AF_INET;
	addrSrv.sin_port = htons(8888);

	bind(sockSrv, (SOCKADDR*)&addrSrv, sizeof(SOCKADDR));

	SOCKADDR_IN addrClient;
	int len = sizeof(SOCKADDR);
	char recvBuf[100] = {0};

	recvfrom(sockSrv, recvBuf, 100, 0, (SOCKADDR*)&addrClient, &len);
	printf("%s\n", recvBuf);
	closesocket(sockSrv);
	WSACleanup();

	system("pause");

	return 0;
}

       服务端程序为：

#include 
#include 
#pragma comment(lib, "ws2_32.lib") 

int main()
{
	WORD wVersionRequested;
	WSADATA wsaData;
	
	wVersionRequested = MAKEWORD(1, 1);
	
	WSAStartup(wVersionRequested, &wsaData);

	SOCKET sockClient = socket(AF_INET, SOCK_DGRAM, 0);
	SOCKADDR_IN addrSrv;
	addrSrv.sin_addr.S_un.S_addr = inet_addr("w.x.y.z"); // 请将w.x.y.z改为实际IP
	addrSrv.sin_family = AF_INET;
	addrSrv.sin_port = htons(8888);

	sendto(sockClient,"test", strlen("test") + 1, 0, (SOCKADDR*)&addrSrv, sizeof(SOCKADDR));
	closesocket(sockClient);
	WSACleanup();

	system("pause");

	return 0;
}

        先启动服务端，再启动客户端，结果：成功通信。啰嗦一句，如果你没有两台电脑，那么你可以用127.0.0.1在同一台电脑上测试。