Winsock网络编程笔记（3）----基于UDP的server和client

在上一篇随笔中，对Winsock中基于tcp面向连接的Server和Client通信进行了说明，但是，Winsock中，Server和Client间还可以通过无连接通信，也就是采用UDP协议。。

因此，这一篇随笔也简单的列举基于UDP的Server和Client的实现。。

和基于TCP的实现相比，其主要的不同点包括：

①接收端（简单地说就是服务器）/发送端（简单地说就是客户端）在创建Socket时候，参数要选择SOCK_DGRAM, IPPROTO_UDP；

②接收端不需要调用listen和accept函数，而是通过recvfrom/WSArecvfrom函数接收数据报；

③发送端通过sendto/WSAsendto接收数据报；

接收端和发送端的代码如下：

 #include"winsock2.h"
 #include<iostream>
 using namespace std;
 //This line is very important

 #pragma comment(lib,"ws2_32.lib")
 int main()
 {
     WSADATA              wsaData;
     SOCKET               ReceivingSocket;
     SOCKADDR_IN          ReceiverAddr;
     int                  Port = ;
     char                 ReceiveBuf[];
     int                  BufLength = ;
     SOCKADDR_IN          SenderAddr;
     int                  SenderAddrSize = sizeof(SenderAddr);
     int                  Ret;

     if ((Ret = WSAStartup(MAKEWORD(,), &wsaData)) != )
     {
         cout<<"WSAStartup failed with error "<<Ret<<endl;
         //here no WSACleanup，because we do not create anything;
         return -;
     }

     // Create a new socket to listening for client connections.
     //Note the difference with TCP
     ReceivingSocket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
     if ( INVALID_SOCKET == ReceivingSocket)
     {
         cout<<"Socket failed with error "<<WSAGetLastError()<<endl;
         WSACleanup();
         return -;
     }

     ReceiverAddr.sin_family = AF_INET;
     ReceiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
     ReceiverAddr.sin_port = htons(Port);

     //to bind
     if (bind(ReceivingSocket, (SOCKADDR *)&ReceiverAddr, sizeof(ReceiverAddr)) == SOCKET_ERROR)
     {
         cout<<"Binding failed with error "<<WSAGetLastError()<<endl;
         closesocket(ReceivingSocket);
         WSACleanup();
         return -;
     }

     // Listen for client connections. We used a backlog of 5 which is
     // normal for many applications.

     cout<<"** We are ready to receive 1 datagram from any interface on port "<<Port<<"**"<<endl;

     //accep a connection when one arrives

     cout<<"** We are waiting for data...**\n";
     //SenderAddrSize = sizeof(SenderAddr);
     Ret = recvfrom(ReceivingSocket,ReceiveBuf,BufLength,,(SOCKADDR *)&SenderAddr,&SenderAddrSize);
     if (SOCKET_ERROR == Ret)
     {
         cout<<"Recvfrom failed with error "<<WSAGetLastError()<<endl;
         closesocket(ReceivingSocket);
         WSACleanup();
         return -;
     }
     cout<<"**We have successfully recieve "<<Ret<<" Byte(s) data!**\n";

     cout<<"**We are going to close the client connection...**\n";

     closesocket(ReceivingSocket);
     WSACleanup();

     return ;
 }

Receiver Code

 #include"winsock2.h"
 #include<iostream>
  #include <time.h>
 using namespace std;
 //This line is very important

 #pragma comment(lib,"ws2_32.lib")
 int main(int argc, char **argv)
 {
     WSADATA              wsaData;
     SOCKET               SendingSocket;
     SOCKADDR_IN          ReceiverAddr;
     int                  Port = ;
     int                  Ret;

     if (argc <= )
     {
         cout<<"USAGE: udpclient <Server IP address>.\n";
         return -;
     }

     // Initialize Winsock version 2.2

     if ((Ret = WSAStartup(MAKEWORD(,), &wsaData)) != )
     {
         cout<<"WSAStartup failed with error "<<Ret<<endl;
         return -;
     }

     // Create a new socket to make a client connection.

     SendingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);//Note the difference with TCP
     if (INVALID_SOCKET == SendingSocket)
     {
         cout << "socket failed with error " << WSAGetLastError()<<endl;
         WSACleanup();
         return -;
     }

     ReceiverAddr.sin_family = AF_INET;
     ReceiverAddr.sin_port = htons(Port);
     ReceiverAddr.sin_addr.s_addr = inet_addr(argv[]);

     // Make a connection to the server with socket s.

     cout<< "We are trying to connect to " << inet_ntoa(ReceiverAddr.sin_addr)
         << ":" << htons(ReceiverAddr.sin_port) << "...\n";

     cout << "We will now try to send a hello message.\n";

     if ((Ret = sendto(SendingSocket, "Hello", , , (SOCKADDR *)&ReceiverAddr,sizeof(ReceiverAddr))) == SOCKET_ERROR)
     {
         cout << "Sendto failed with error " << WSAGetLastError()<<endl;
         closesocket(SendingSocket);
         WSACleanup();
         return -;
     }

     cout << "We successfully sent " << Ret << " byte(s).\n";

     // When you are finished sending and receiving data on socket s,
     // you should close the socket.

     cout << "We are closing the connection.\n";

     closesocket(SendingSocket);

     // When your application is finished handling the connection, call
     // WSACleanup.

     WSACleanup();
     return ;
 }

Sender Code