基于UDP的Sockets编程

#include<winsock2.h>
#include<stdio.h>
#include<windows.h>
#pragma comment(lib,"WS2_32.lib")
int main()
{
    WSADATA data;
    WORD w=MAKEWORD(2,0);
    char sztext[]="欢迎你\r\n";
    ::WSAStartup(w,&data);
    SOCKET s;
    s=::socket(AF_INET,SOCK_DGRAM,0);
    sockaddr_in addr,addr2;
    int n=sizeof(addr2);
    char buff[11]={0};
    addr.sin_family=AF_INET;
    addr.sin_port=htons(75);
    addr.sin_addr.S_un.S_addr=INADDR_ANY;
    ::bind(s,(sockaddr*)&addr,sizeof(addr));
    printf("UDP服务器已经启动\r\n");
while(1)
{
    if(::recvfrom(s,buff,11,0,(sockaddr*)&addr2,&n)!=0)
    {
        printf("%s已经连接上\r\n",inet_ntoa(addr2.sin_addr));
        printf("%s\r\n",buff);
        ::sendto(s,sztext,sizeof(sztext),0,(sockaddr*)&addr2,n);
          break;
        } 
}
            ::closesocket(s);
            ::WSACleanup();
           if(getchar())                        //如果有输入则关闭程序
          {
          return 0;                        //正常结束程序
            }
          else
          {::Sleep(100);
            }

}

#include<winsock2.h>
#include<stdio.h>
#include<windows.h>
#pragma comment(lib,"WS2_32.lib")
int main()
{
    WSADATA data;
    WORD w=MAKEWORD(2,0);
    char sztext[]="服务器，你好!\r\n";
    ::WSAStartup(w,&data);
    SOCKET s;
    s=::socket(AF_INET,SOCK_DGRAM,0);
    sockaddr_in addr,addr2;
    int n=sizeof(addr2);
    char buff[10]={0};
    addr.sin_family=AF_INET;
    addr.sin_port=htons(75);
    addr.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");
    printf("UDP客户端已经启动\r\n");
    if(::sendto(s,sztext,sizeof(sztext),0,(sockaddr*)&addr,n)!=0)
        {
        ::recvfrom(s,buff,10,0,(sockaddr*)&addr2,&n);
        printf("服务器说：%s\r\n",buff);
        ::closesocket(s);
            ::WSACleanup();
                    } 
           if(getchar())                        //如果有输入则关闭程序
          {
          return 0;                        //正常结束程序
            }
          else
          {::Sleep(100);
            }

}