delphi – 使用SO_REUSEADDR时,接收UDP数据包发送到127.0.0.1

FBroadcastSocket := socket( AF_INET,SOCK_DGRAM,IPPROTO_UDP );
if FBroadcastSocket = INVALID_SOCKET then Exit;
i := 1;
setsockopt( FBroadcastSocket,SOL_SOCKET,SO_REUSEADDR,Pointer( @i ),sizeof( i ) );
i := 1;
setsockopt( FBroadcastSocket,SO_BROADCAST,sizeof( i ) );
System.FillChar( A,sizeof( A ),0 );
A.sin_family      := AF_INET;
A.sin_port        := htons( FBroadcastPort );
A.sin_addr.S_addr := INADDR_ANY;
if bind( FBroadcastSocket,A,sizeof( A ) ) = SOCKET_ERROR then begin
    CloseBroadcastSocket();
    Exit;
end;
WSAEventSelect( FBroadcastSocket,FBroadcastEvent,FD_READ );

for i := 0 to High( FBroadcastAddr ) do begin
    if sendto( FBroadcastSocket,FBroadcastData[ 0 ],Length( FBroadcastData ),FBroadcastAddr[ i ],sizeof( FBroadcastAddr[ i ] ) ) < 0 then begin
        TLogging.Error( C_S505,[ GetWSAError() ] );
    end;
end;

procedure TSocketHandler.DoRecieveBroadcast();
var
    RemoteAddr:    TSockAddrIn;
    i,N:          Integer;
    NetworkEvents: WSANETWORKEVENTS;
    Buffer:        TByteDynArray;
begin
    // Sanity check.
    FillChar( NetworkEvents,sizeof( NetworkEvents ),0 );
    WSAEnumNetworkEvents( FBroadcastSocket,@NetworkEvents );
    if NetworkEvents.ErrorCode[ FD_READ_BIT ] <> 0 then Exit;

    // Recieve the broadcast buffer
    i := sizeof( RemoteAddr );
    SetLength( Buffer,MaxUDPBufferSize );
    N := recvfrom( FBroadcastSocket,Buffer[ 0 ],Length( Buffer ),RemoteAddr,i );
    if N <= 0 then begin
        N := WSAGetLastError();
        if N = WSAEWOULDBLOCK then Exit;
        if N = WSAEINTR then Exit;
        TLogging.Error( C_S504,[ GetWSAError() ] );
        Exit;
    end;

    DoProcessBroadcastBuffer( Buffer,N,inet_ntoa( RemoteAddr.sin_addr ) );
end;

看起来你想要的是硬编码广播地址而不用担心机器正在使用什么实际的IP地址.您的第一个问题是,由于这是一个新的应用程序,您应该使用多播而不是广播.然后,您可以使用特殊的多播地址,无论机器实际具有什么地址,它都可以在任何地方使用.我假设所有这些应用程序都在同一台机器上运行.

这是一个用Perl编写的示例程序.您应该能够非常轻松地调整代码.在不同的窗口中开始几个副本,看看它是如何工作的.基本上它会分发发件人和收件人,并发送发件人的日期时间和pid.您需要从CPAN安装Socket :: Multicast包才能运行它.

#!/usr/bin/perl -w
# This example is a reimplementation of Steven's sendrecv Multicast example from UNP
use strict;
use diagnostics;
use Socket;
use Socket::Multicast qw(:all); # Has to be installed from CPAN

my $sendSock;

socket($sendSock,PF_INET,getprotobyname('udp'))   
    || die "socket: $!";
setsockopt($sendSock,pack("l",1))   
    || die "setsockopt: $!";
# create socket with ephemeral port for sending $port = 0
bind($sendSock,sockaddr_in(0,INADDR_ANY))  || die "bind: $!"; 

# create socket for multicast receive
my $recvSock;
my $mcastIP = '239.255.1.2';
my $mcastPort = 9999;

socket($recvSock,getprotobyname('udp'))   
   || die "socket: $!";
setsockopt($recvSock,1))   
   || die "setsockopt: $!";

# join to specific port and IPV4 address to select mcast interface
my $imr_multicast = inet_aton($mcastIP);
my $imr_interface = INADDR_ANY;
my $ip_mreq = pack_ip_mreq($imr_multicast,$imr_interface);
my $ip = getprotobyname( 'ip' );

setsockopt($recvSock,$ip,IP_ADD_MEMBERSHIP,$ip_mreq)     
    || die "setsockopt IP_ADD_MEMBERSHIP failed: $!";

# bind to multicast address to prevent reception of unicast packets on this port
bind($recvSock,sockaddr_in($mcastPort,inet_aton($mcastIP)))  || die "bind: $!"; 

# disable multicast loopback so I don't get my own packets
# only do this if you're running instances on seperate machines otherwise you won't
# get any packets
# setsockopt( $recvSock,IP_MULTICAST_LOOP,pack( 'C',$loop ) ) 
  #  || die( "setsockopt IP_MULTICAST_LOOP failed: $!" );

# fork sender and receiver
my $pid = fork();
if ( $pid == 0) {
    mrecv();
} else {
    msend();
}    

sub msend {
    close($recvSock);
    while (1) {
        my $datastring = `date`; chomp($datastring);
        $datastring = "$datastring :: $pidn";
        my $bytes = send($sendSock,$datastring,inet_aton($mcastIP)));
        if (!defined($bytes)) { 
            print("$!n"); 
        } else { 
            print("sent $bytes bytesn"); 
        }
        sleep(2);
    }
}

# just loop forever listening for packets
sub mrecv {
    close($sendSock);
    while (1) {
        my $datastring = '';
        my $hispaddr = recv($recvSock,64,0); # blocking recv
        if (!defined($hispaddr)) {
            print("recv failed: $!n");
            next;
        }
        print "$datastring";
    }
}