UDP broadcast package on win7

最新推荐文章于 2024-07-08 10:29:00 发布

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最新推荐文章于 2024-07-08 10:29:00 发布

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分类专栏： network 文章标签： broadcast udp win7 socket

本文链接：https://blog.youkuaiyun.com/huangweiliang/article/details/45193423

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本文提供了一个Windows环境下发送广播包到指定IP的完整代码示例，解决了win7及以上系统中广播包源IP限制的问题。

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由于工作需要，我需要实现一个UDP发送广播包到设备的需求。如果是linux下，那很简单。但是上位机要求是windows.

网上简单搜了一下，代码很多。可我发现就是没办法在设备端收到我发送的广播包。

都不用检查防火墙，我电脑的防火墙早关了。

后来看到stackoverflow.com上面有人也遇到了同样的问题，但是没有给出具体的例子快哭了

简单来说原因是这样的：win7之前的系统，发送广播包是到pc所有的网卡上的。 win7及以后，是要求制定广播包的源IP.简单说bind的IP不能是INADDR_ANY.

下面的例子是可以工作的。

注：%99代码是网上的，我只改了几行。

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

int main(int argc, char *argv[])
{
    SOCKET s;
    struct sockaddr_in server, si_other;
    int slen ;

    WSADATA wsa;

    slen = sizeof(si_other) ;

    //Initialise winsock
    printf("\nInitialising Winsock...");
    if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
    {
        printf("Failed. Error Code : %d",WSAGetLastError());
        exit(EXIT_FAILURE);
    }
    printf("Initialised.\n");

    //Create a socket
    if((s = socket(AF_INET , SOCK_DGRAM , 0 )) == INVALID_SOCKET)
    {
        printf("Could not create socket : %d" , WSAGetLastError());
    }
    printf("Socket created.\n");
     int so_broadcast = TRUE;
    setsockopt(s, SOL_SOCKET, SO_BROADCAST, (char *)&so_broadcast, sizeof(so_broadcast));
    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
   /* the card IP of the PC*/
   printf("send BC package on the port with IP %s\n", argv[1]);
    server.sin_addr.s_addr = inet_addr(argv[1]);   -----------------> SPECIFIC THE IP HERE
    server.sin_port = htons( 9989 );

    //Bind
    if( bind(s ,(struct sockaddr *)&server , sizeof(server)) == SOCKET_ERROR)
    {
        printf("Bind failed with error code : %d" , WSAGetLastError());
        exit(EXIT_FAILURE);
    }
    puts("Bind done");
     si_other.sin_family = AF_INET;
    si_other.sin_addr.S_un.S_addr =htonl(INADDR_BROADCAST);
   //unsigned long ip = inet_addr("172.17.255.255");
   //b_addr.sin_addr.S_un.S_addr =htonl(ip);
    si_other.sin_port = htons(9988);
    //keep listening for data
    while(1)
    {


        //buf the buffer by filling null, it might have previously received data
        char buf[128] = "ADD YOUR PAYLOAD HERE";



        //now reply the client with the same data
        if (sendto(s, buf, strlen(buf), 0, (struct sockaddr*) &si_other, slen) == SOCKET_ERROR)
        {
            printf("sendto() failed with error code : %d" , WSAGetLastError());
            exit(EXIT_FAILURE);
        }
       printf("send... %d\n", WSAGetLastError());
       Sleep(1000);

    }

    closesocket(s);
    WSACleanup();

    return 0;
}