不講解了，要求讀者：
1. 知道UDP是什麼
2. 索求Windows環境下的socket程式設計函式
3. 已經配置好了編譯環境——在Tools-option-中的設定

客戶端程式碼

#include <stdio.h>
#include <winsock2.h>
#include <iostream> 
#pragma comment(lib, "ws2_32.lib") 
using namespace std;

bool BindSocket(SOCKET& socket,short port ,const char* Ip){
    sockaddr_in address;
    address.sin_family=AF_INET;
    address.sin_addr.s_addr =inet_addr(Ip);
    address.sin_port=htons(port);
    if
 
(SOCKET_ERROR == bind(socket,(const struct sockaddr*)&address,sizeof(struct sockaddr)) ){
        return false;
    } 
    return true;
}

int main()
{
    WORD wVersionRequested;
    WSADATA wData;
    int err;
    int port;               //客戶端埠號 
    int Otherport;          //伺服器埠號 
    char IPaddr[18
 
];        //客戶端Ip 
    char OtherIP[18];       //伺服器Ip 
    wVersionRequested = MAKEWORD( 1, 1 );   // 請求WinSock庫
    err = WSAStartup( wVersionRequested, &wData );
    if(err!=0)  {return -1;}                // 返回值為零時表示成功WSAStartup

    SOCKET sockCli = socket(AF_INET, SOCK_DGRAM, 0);        //建立Socket 
    if
 
(sockCli < 0){
        cout << "socket creation failed" << endl;
        return 0; 
    } 
    cout << "socket created" << endl;

    cout << "請輸入本機IP：" << endl;     //輸入客戶端IP和埠號 
    gets(IPaddr);
    printf("請輸入本機埠號:\n");
    cin >> port;

    if(!BindSocket(sockCli,port,IPaddr)){   //將本地IP地址和埠號繫結到所建立的套接字上
        cout << "Bind failed" << endl;
        return 0; 
    } 
    cout << "Bind Socket success " << endl;

    sockaddr_in address;                //伺服器的IP和埠號 
    cout << "請輸入伺服器的IP" << endl;
    cin >> OtherIP;
    cout << "請輸入伺服器的埠號"  << endl;
    cin >> Otherport;
    address.sin_family=AF_INET;
    address.sin_addr.s_addr=inet_addr(OtherIP); 
    address.sin_port=htons(Otherport);


    char talk[100]="t"; 
    for(int i=0;i<100;i++){         //傳送100個數據包 
        sendto(sockCli,talk, sizeof(talk), 0,(const struct sockaddr*)&address,sizeof(struct sockaddr) );
    }


    closesocket(sockCli); 
    WSACleanup(); 

    return 0; 
}

伺服器程式碼：

#include <stdio.h>
#include <iostream>
// c++ include lib from windows
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib") 
using namespace std;

bool BindSocket(SOCKET& socket,short port ,const char* Ip){
    sockaddr_in address;
    // set address of socket from socket family AF_INET;
    address.sin_family=AF_INET;
    address.sin_addr.s_addr =inet_addr(Ip);// set machine IP; 
    address.sin_port=htons(port);   // set machine port
    // all above belong to net words;
    if(SOCKET_ERROR == bind(socket,(const struct sockaddr*)&address,sizeof(struct sockaddr)) ){
        return false;
    } 
    return true;
}

int main()
{
    WORD wVersionRequested;
    WSADATA wsaData;
    int err;
    int port;           //伺服器埠號 
    char IPaddr[18];    //伺服器Ip 
    sockaddr_in address;
    int n=sizeof(struct sockaddr);
    char talk[100]={0};
    char buffer[100] = {0};
    wVersionRequested = MAKEWORD( 1, 1 );   // 請求WinSock庫  
    err = WSAStartup( wVersionRequested, &wsaData );
    if(err!=0)  {return -1;} 

    SOCKET sockSrv = socket(AF_INET, SOCK_DGRAM, 0);        //建立Socket 
    /* Something about socket return value. */
    if(sockSrv < 0){
        cout << "socket creation failed" << endl;
        return 0;
    }
    cout << "socket created" << endl;

    cout << "請輸入本機IP：" << endl;
    cin >> IPaddr;
    printf("請輸入本機埠號:\n");
    cin >> port;
    //cout << IPaddr << endl << port << endl;
    while(! BindSocket(sockSrv,port,IPaddr)){       //將本地IP地址和埠號繫結到所建立的套接字上 
        cout << "Bind fail" << endl;
        cout << "請輸入本機IP：" << endl;
        cin >> IPaddr;
        printf("請輸入本機埠號:\n");
        cin >> port;
    }
    cout << "Bind Socket success " << endl;

    /*這裡不知道對不對*/ 


    int num =0;
    // over-time setting, and ACKpp setting;
    // more about recvfrom function;
    while(1){           //接受來自客戶端的資料包 
        if(recvfrom(sockSrv,buffer, 100,0,(struct sockaddr*)&address,&n) == SOCKET_ERROR ) {
            cout << "接收失敗"  << endl; 
        }
        else{
                num++;
        }
        cout << num << endl;// output situation;
    }

    closesocket(sockSrv); 
    WSACleanup(); 
    return 0;
}