用C++创建一个简单的UDP客户端

#include <WinSock2.h>
#include <Windows.h>
#include <iostream>
#pragma comment(lib,"ws2_32.lib")
using namespace std;

int main() 
{
  WSADATA d;
  WORD w = MAKEWORD(2, 0);
  WSAStartup(w, &d);

  SOCKET s = socket(AF_INET, SOCK_DGRAM, 0);
  sockaddr_in serverAddr;
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
  serverAddr.sin_port = htons(9999);
  int len = sizeof(serverAddr);
  char buf[] = "Hello,UDP server!";
  sendto(s, buf, sizeof(buf), 0, (sockaddr*)&serverAddr,len);

  char recvBuf[512] = { 0 };
  int recvLen = recvfrom(s, recvBuf, 512, 0, (sockaddr*)&serverAddr, &len);
  if (recvLen > 0) {
    cout << recvBuf << endl;
  }

  getchar();
  closesocket(s);
  WSACleanup();
  return 0;
}