Udp

基于无连接的Udp编程.

代码注释，如下：

//Server.cpp
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")

#define BUF_SIZE 64

int main()
{
    WSADATA wsadata; //包含DLL期望程序使用的版本和支持的最高版本等字段
    int retVal;

    SOCKET sServer;
    char buf[BUF_SIZE];

    //加载套接字DLL
    retVal=WSAStartup(MAKEWORD(2,2),&wsadata);
    if(retVal != 0)
    {
        printf("WSAStartup failed!\n");
    }

    //创建套接字
    sServer=socket(AF_INET,SOCK_DGRAM,IPPROTO_IP);
    if(sServer == INVALID_SOCKET)
    {
        printf("socket failed!\n");

        WSACleanup();
        return -1;
    }

    //绑定套接字(绑定套接字时，需要明确指出服务器的各个地址字段)
    SOCKADDR_IN addrServ;
    addrServ.sin_family=AF_INET; //套接字属于协议族TCP/IP
    addrServ.sin_port=htons(4999);
    addrServ.sin_addr.S_un.S_addr=INADDR_ANY;

    retVal=bind(sServer,(LPSOCKADDR)&addrServ,sizeof(SOCKADDR_IN));
    if(retVal == SOCKET_ERROR)
    {
        printf("bind failed!\n");

        closesocket(sServer);
        WSACleanup();
        return -1;
    }



    //接收数据
    SOCKADDR_IN addrClient;  //接收数据时，系统自动填充地址字段
    int len=sizeof(SOCKADDR_IN);

    ZeroMemory(buf,BUF_SIZE);

    retVal=recvfrom(sServer,buf,BUF_SIZE,0,(LPSOCKADDR)&addrClient,&len);
    if(retVal == SOCKET_ERROR)
    {
        printf("recvfrom failed!\n");

        closesocket(sServer);
        WSACleanup();
        return -1;
    }

    //
    printf("Server receives data: ");
    printf("%s\n",buf);

    //
    closesocket(sServer);
    WSACleanup();
    return 0;
}

 

//Client.cpp
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")

#define BUF_SIZE 64

int main()
{
    WSADATA wsadata;
    int retVal;

    SOCKET sClient;
    char buf[BUF_SIZE];


    //加载套接字DLL
    retVal=WSAStartup(MAKEWORD(2,2),&wsadata);
    if(retVal != 0)
    {
        printf("WSAStartup failed!\n");
    }

    //创建套接字
    sClient=socket(AF_INET,SOCK_DGRAM,IPPROTO_IP);
    if(sClient == INVALID_SOCKET)
    {
        printf("socket failed!\n");

        WSACleanup();
        return -1;
    }


    //发送数据(发送数据时，需要明确指出服务器的各个地址字段)
    SOCKADDR_IN addrServ;
    addrServ.sin_family=AF_INET; //套接字属于协议族TCP/IP
    addrServ.sin_port=htons(4999);
    addrServ.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");

    ZeroMemory(buf,BUF_SIZE);
    strcpy(buf,"Hello Udp!");

    retVal=sendto(sClient,buf,BUF_SIZE,0,(LPSOCKADDR)&addrServ,sizeof(SOCKADDR_IN));
    if(retVal == SOCKET_ERROR)
    {
        printf("sendto failed!\n");

        closesocket(sClient);
        WSACleanup();
        return -1;
    }

    //
    closesocket(sClient);
    WSACleanup();
    return 0;
}

 

*************************************************************************

补充说明：

1.

#define INVALID_SOCKET  (SOCKET)(~0)
#define SOCKET_ERROR            (-1)

#define INADDR_ANY              (u_long)0x00000000

 

#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib") //#pragma comment(Comment-Type,"CommentString")

①头文件，只有函数的声明；（编译阶段连接进去）②库文件，如果有DLL，则充当索引的作用；如果没有，则包含函数的实现代码；（链接阶段）③DLL，在运行阶段，把函数的实现代码连接进去.

2.

 

typedef struct WSAData {
  WORD wVersion; //系统希望程序使用的库版本
  WORD wHighVersion; //系统支持的最高版本
  char szDescription[WSADESCRIPTION_LEN+1];
  char szSystemStatus[WSASYS_STATUS_LEN+1];
  unsigned short iMaxSockets;
  unsigned short iMaxUdpDg;
  char FAR* lpVendorInfo;
} WSADATA, 
*LPWSADATA;

3.

 

int WSAStartup(
  WORD wVersionRequested,
  LPWSADATA lpWSAData
);
Return Values
The WSAStartup function returns zero if successful. Otherwise, it returns one of the error codes listed in the following.(WSASYSNOREADY | WSAEFAULT)

 4.

对于main()函数而言，返0，则表示成功执行；返其它，则表示程序执行异常.

*************************************************************************

 

函数原型：

1.

int sendto(
  SOCKET s,
  const char* buf,
  int len,
  int flags,
  const struct sockaddr* to,
  int tolen
);

int flags, //MSG_OOB | MSG_DONTROUTE

 

int flags, //MSG_OOB | MSG_PEEK

int recvfrom(
  SOCKET s,
  char FAR* buf,
  int len,
  int flags,
  struct sockaddr FAR* from,
  int FAR* fromlen
);