这两天很多人在问怎么样用SOCKET实现广播（BoardCast）

正好我做过这方面的程序，这里用最简单的代码写一个广播发送和接受的例子：

//////

//发送端程序

#include <stdio.h>
#include <winsock.h>

int main(int argc, char* argv[])
{
    WSADATA wsaData;          //指向WinSocket信息结构的指针
    SOCKET sockListener;
    SOCKADDR_IN sin,saUdpServ;
    BOOL fBroadcast = TRUE;
    char sendBuff[1024];
    int nSize;
    int ncount=0;
    if(WSAStartup(MAKEWORD( 1, 1 ), &wsaData )!=0)//进行WinSocket的初始化
    {
        printf("Can't initiates windows socket!Program stop.\n");//初始化失败返回-1
        return -1;
    }
    sockListener=socket(PF_INET,SOCK_DGRAM,0);
    setsockopt ( sockListener,SOL_SOCKET,SO_BROADCAST,

        (CHAR *)&fBroadcast,sizeof ( BOOL ));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(0);
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
    if(bind( sockListener, (SOCKADDR *)&sin, sizeof(sin))!=0)
    {
        printf("Can't bind socket to local port!Program stop.\n");//初始化失败返回-1
        return -1;
    }
    saUdpServ.sin_family = AF_INET;
    saUdpServ.sin_addr.s_addr = htonl ( INADDR_BROADCAST );
    saUdpServ.sin_port = htons (7001);//发送用的端口，可以根据需要更改
    nSize = sizeof ( SOCKADDR_IN );
    while(1)
    {
        sprintf(sendBuff,"Message %d",ncount++);
        sendto ( sockListener,sendBuff,
            lstrlen (sendBuff),
            0,
            (SOCKADDR *) &saUdpServ,
            sizeof ( SOCKADDR_IN ));
        printf("%s\n",sendBuff);
    }
return 0;
}

/////////////////////

//接收

#include <stdio.h>
#include <winsock.h>
#include <conio.h>

int main(int argc, char* argv[])
{
    WSADATA wsaData;          //指向WinSocket信息结构的指针
    SOCKET sockListener;
    SOCKADDR_IN sin,saClient;
    char cRecvBuff[1024];
    int nSize,nbSize;
    int iAddrLen=sizeof(saClient);
    if(WSAStartup(MAKEWORD( 1, 1 ), &wsaData )!=0)//进行WinSocket的初始化
    {
        printf("Can't initiates windows socket!Program stop.\n");//初始化失败返回-1
        return -1;
    }
    sockListener=socket(AF_INET, SOCK_DGRAM,0);
    sin.sin_family = AF_INET;
    sin.sin_port = htons(7001);//发送端使用的发送端口，可以根据需要更改
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
    if(bind( sockListener, (SOCKADDR FAR *)&sin, sizeof(sin))!=0)
    {
        printf("Can't bind socket to local port!Program stop.\n");//初始化失败返回-1
        return -1;
    }
    while(1)
    {
        nSize = sizeof ( SOCKADDR_IN );
        if((nbSize=recvfrom (sockListener,cRecvBuff,1024,0,

            (SOCKADDR FAR *) &saClient,&nSize))==SOCKET_ERROR)
        {
            printf("Recive Error");
            break;
        }
        cRecvBuff[nbSize] = '\0';
        printf("%s\n",cRecvBuff);

    }
    return 0;
}