用udp协议通讯示例

作者：fs007

下载源代码

一、绪言
　　udp是一种面向非连接，不可靠的通讯协议，相对于tcp来说，虽然可靠性不及，但传输效率较高。所以在网络上仍有很大的用途。这几日需要了解下udp通讯的过程，上网发现这方面的资料还挺少。于是仔细的翻找了下msdn,基本上搞清楚了udp通讯的过程。做了一个测试的例子。希望对大家有帮助。

二、udp的通讯过程

server端: open a socket(socket)--->name the socket(bind)--->send and receive data(sendto recvfrom)--->close socket(closesocket)
client端: open a socket(socket)---------------------------->send and receive data(sendto recvfrom)--->close socket(closesocket)

　　server端无需listen，client端无需connect，因此udp中server和client的区别相对较模糊。只要调用sendto和recvfrom就可以给指定的地址收发数据，但并不保证收发的数据的完整性和可靠性。

三、示例
　　udpserver主要代码：

void main()
{
	SOCKET socket1;

	InitWinsock();
	struct sockaddr_in local;
	struct sockaddr_in from;
	int fromlen =sizeof(from);
	local.sin_family=AF_INET;
	local.sin_port=htons(1000);             ///监听端口
	local.sin_addr.s_addr=INADDR_ANY;       ///本机

	socket1=socket(AF_INET,SOCK_DGRAM,0);
	bind(socket1,(struct sockaddr*)&local,sizeof local);
	while (1)
	{
		char buffer[1024]="\0";
		printf("waiting for message from others-------------\n");
		if (recvfrom(socket1,buffer,sizeof buffer,0,(struct sockaddr*)&from,&fromlen)!=SOCKET_ERROR)
		{
			printf("Received datagram from %s--%s\n",inet_ntoa(from.sin_addr),buffer);
			////给cilent发信息
			sendto(socket1,buffer,sizeof buffer,0,(struct sockaddr*)&from,fromlen);

		}
		Sleep(500);
	}
	closesocket(socket1);
}

void main()
{
	SOCKET socket1;

	InitWinsock();
	struct sockaddr_in server;
	int len =sizeof(server);
	server.sin_family=AF_INET;
	server.sin_port=htons(1000);                      ///server的监听端口
	server.sin_addr.s_addr=inet_addr("168.168.0.10"); ///server的地址 

	socket1=socket(AF_INET,SOCK_DGRAM,0);
	while (1)
	{
		char buffer[1024]="\0";
		printf("input message\n");
		scanf("%s",buffer);
		if (strcmp(buffer,"bye")==0)
			break;
		if (sendto(socket1,buffer,sizeof buffer,0,(struct sockaddr*)&server,len)!=SOCKET_ERROR)
		{	
			if (recvfrom(socket1,
                                        buffer,
                                        sizeof buffer,
                                        0,
                                        (struct sockaddr*)&server,&len) != SOCKET_ERROR)
				printf("rece from server:%s\n",buffer);
		}		
	}
	closesocket(socket1);
}