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 = 5150;
    char                 ReceiveBuf[1024];
    int                  BufLength = 1024;
    SOCKADDR_IN          SenderAddr;
    int                  SenderAddrSize = sizeof(SenderAddr);
    int                  Ret;

    if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)
    {
        cout<<"WSAStartup failed with error "<<Ret<<endl;
        //here no WSACleanup，because we do not create anything;
        return -1;
    }

    // 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 -1;
    }

    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 -1;
    }

    // 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...**
";
    //SenderAddrSize = sizeof(SenderAddr);
    Ret = recvfrom(ReceivingSocket,ReceiveBuf,BufLength,0,(SOCKADDR *)&SenderAddr,&SenderAddrSize);
    if (SOCKET_ERROR == Ret)
    {
        cout<<"Recvfrom failed with error "<<WSAGetLastError()<<endl;
        closesocket(ReceivingSocket);
        WSACleanup();
        return -1;
    }
    cout<<"**We have successfully recieve "<<Ret<<" Byte(s) data!**
";

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

    closesocket(ReceivingSocket);
    WSACleanup();

    return 0;
}

#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 = 5150;
    int                  Ret;

    if (argc <= 1)
    {
        cout<<"USAGE: udpclient <Server IP address>.
";
        return -1;
    }

    // Initialize Winsock version 2.2

    if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)
    {
        cout<<"WSAStartup failed with error "<<Ret<<endl;
        return -1;
    }

    // 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 -1;
    }

    ReceiverAddr.sin_family = AF_INET;
    ReceiverAddr.sin_port = htons(Port);    
    ReceiverAddr.sin_addr.s_addr = inet_addr(argv[1]);

    // 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) << "...
";

    cout << "We will now try to send a hello message.
";
        
    if ((Ret = sendto(SendingSocket, "Hello", 5, 0, (SOCKADDR *)&ReceiverAddr,sizeof(ReceiverAddr))) == SOCKET_ERROR)
    {
        cout << "Sendto failed with error " << WSAGetLastError()<<endl;
        closesocket(SendingSocket);
        WSACleanup();
        return -1;
    }
    
    cout << "We successfully sent " << Ret << " byte(s).
";
    
    // When you are finished sending and receiving data on socket s,
    // you should close the socket.

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

    closesocket(SendingSocket);

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

    WSACleanup();
    return 0;
}