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LAN-Browser

Started by stryx Dec 8, 2002 at 8:02 AM 7 replies 1.1k views

Original Post

Dec 8, 2002 at 8:02 AM

I know this question was asked before lots of times, but the answeres didn''t help me much. The problem is I have to code a ServerBrowser for LAN and I''ve no idea how to do this. I read in this forum, that Broadcasting is the way to do this. I have to create a Broadcasting Socket @ the server. Then the client sends to the ip 255.255.255.255 an requesting-servers message, and all the servers with the broadcast sockets should get this, and reply. Am I right with this ? It woulb be very nice if someone here can hack a small piece of code together (tutorial would be perfect for this page) and post it somewhere. If you got no space, mail me, I''ll host it. It would be nice if you can point me somewhere. thanks stryx stryx@gmx.at Thanks in advance.

wrathgame

Dec 11, 2002 at 8:53 AM

Elo,

You may get more help if you explain more what it is exactly that you want to do ??

You can use the UDP protocal to broadcast to all available IP addresses by sending it to 255.255.255.255 but that will only be forwarded by some network hubs/switchs like for example the internet doesnt forward 255.255.255.255 broadcasts

try giving an example of your problem

stryx

Author

stryx

Dec 11, 2002 at 1:44 PM

Ok here''s what i want to do.

This is only for LAN !

Server A creates a game.
Client A wants to join but doesn''t know the IP of the server.
So the client has to broadcast if there is a server on the network.
If a server recv''s this message he replys with his data.
So the client gets a list of the servers available on the network.
Like the server-browser in Quake 3

How to set up the client socket to broadcast, and how to set up the server socket to recv the broadcast ?

Karg

Dec 11, 2002 at 2:00 PM

Not that your idea won''t work, or that mine is even any better, but I had the servers broadcast every sec. or so and the client would just listen on the port when the program starts up and build up a list of servers it has heard from. Then it would drop a server it hadn''t heard from in a few secs. Just have the server send an "I''m here" packet every sec. and have the clients constantly recv. on the "server searching" port when it is at the splash screen/main menu/config/anything else not in game portion.

Karg

stryx

Author

stryx

Dec 11, 2002 at 4:59 PM

you''re right.
That''s a fine idea, too.
Better than mine, but I think it''s more bandwidth waste than mine.
Am I right ?

Well, the "MAIN-PROBLEM" is, that I don''t know how to send and recv this messages.
I know that I have to set a socket (server or client) to SO_BROADCAST or somethuing like that.

These lines for the setup and sending of the messages of both server and client are the problem.

Would be great if somebody can drop this lines here

thanks anyway, stryx

Shannon Barber

Mod

368

Shannon Barber

Dec 11, 2002 at 5:11 PM

Which method uses more bandwidth depend on the number of clients. If there are lots of clients, the second way may actually use less bandwidth.

But it doesn''t matter - one tiny, tiny packet sent once a second won''t make a big difference on a LAN.

I think I would only broad-cast it to the server''s subnet though.
e.g. server address:
ip: 192.168.0.1
mask: 255.255.255.0

broadcast to: 192.168.0.255

wrathgame

Dec 11, 2002 at 7:20 PM

Ok.. I think your gagging for some code so here ya go

Client (broadcasts)

  
  sockaddr_in sa;
  int s;
  int n = sizeof(sockaddr);
  int on = 1;
  int len = strlen(argv[1]);

  if ( (s = socket(AF_INET,SOCK_DGRAM,0)) < 0 )
    exit(-1);

// broadcast option

  if ( setsockopt(s, SOL_SOCKET, SO_BROADCAST, (void *)&on, sizeof(on)) != 0)
    exit(-2);

  sa.sin_family = AF_INET;
// 255.255.255.255

  sa.sin_addr.s_addr = htonl(INADDR_BROADCAST);
  sa.sin_port = htons(1234);
  sendto(s, argv[1], len, 0, (const struct sockaddr *)&sa, n);
}

Server (recieves)

  
  struct sockaddr_in sa;
  int s;
  int i;
  int n = sizeof(struct sockaddr);
  char buf[256];
  hostent *hp;

  if ( (s = socket(AF_INET,SOCK_DGRAM,0)) < 0 )
    exit(-1);

  sa.sin_family = AF_INET;
// any address

  sa.sin_addr.s_addr = htonl(INADDR_ANY);
  sa.sin_port = htons(1234);

  if ( bind(s, (struct sockaddr *) &sa, n ) != 0 )
    exit(1);
  while ( 1 )
  {
    if ( (i=recvfrom(s,buf,255,0,(struct sockaddr *)&sa,&n)) == -1 )
        exit(1);
    buf[i] = (char)0;
    hp = gethostbyaddr((const char *)&sa.sin_addr, 4, AF_INET);
    cout << hp->h_name << ": " << buf << endl;
  }