I have no problems with CreateSession() and JoinSession() when the host starts the server. I get the exception mentioned in the subject when another network gamer tries to join the session. Specifically in the GamerJoinedEventHandler inside the else statement during the cast. Am I going about this the wrong way? All gamers are on separate machines.

private LocalNetworkGamer server;

private LocalNetworkGamer localGamer;

public void CreateSession()

{

try

{

networkSession =

NetworkSession.Create(NetworkSessionType.SystemLink,

NetworkGlobals.MAX_LOCAL_GAMERS,

NetworkGlobals.MAX_GAMERS);

networkSession.GamerJoined += GamerJoinedEventHandler;

networkSession.SessionEnded += SessionEndedEventHandler;

}

catch (System.Exception e)

{

// Error handling removed for brevity

}

}

public void JoinSession()

{

try

{

// Search for sessions.

using (AvailableNetworkSessionCollection availableSessions =

NetworkSession.Find(NetworkSessionType.SystemLink,

NetworkGlobals.MAX_LOCAL_GAMERS, null))

{

if (availableSessions.Count == 0)

{

throw new System.Exception("No sessions found");

}

// Join the first session we find.

networkSession = NetworkSession.Join(availableSessions[0]);

networkSession.GamerJoined += GamerJoinedEventHandler;

networkSession.SessionEnded += SessionEndedEventHandler;

}

}

catch (System.Exception e)

{

throw e;

}

}

private void GamerJoinedEventHandler(object sender, GamerJoinedEventArgs e)

{

if (e.Gamer.IsHost)

{

server = (LocalNetworkGamer) e.Gamer;

}

else

{

localGamer = (LocalNetworkGamer) e.Gamer;

}

Player player = new Player(e.Gamer);

e.Gamer.Tag = player;

}

I believe I have found my problem. I'm still learning to use the debug features of VS and it took me this long to do it old school with sysouts. Copy and paste is a b... east! I duplicated the  event handler code in JoinSession. I removed

Yes you are doing this wrong. First off you do not need to store the variables server or localGamer. The entire gamerJoinedEventHandler should just be on line setting the gamer tag as a new player.

Thank you for your response. The Client Server example updates everyone with everything. I do not have that same requirement. I need to be more selective. The 'want' or need for me to store localGamer and server saves me from having to cast in multiple areas of my code. If I want the server to send a message, then I cannot simply use networkSession.Host.Send.... as I will have to cast the Host to a LocalNetworkGamer. It's working just fine for me now such that I can prove my concept. If I ever actually do something with the code, then you can bet I'll be back with more questions. Thanks again.

The problem is you are assuming that all gamers will be LocalNetworkGamer instances. That isn't true as soon as you have more than one machine in the session!  You can only cast to LocalNetworkGamer if that gamer is indeed local, so you need to check that before doing the cast.  For instance the host gamer will only also be a LocalNetworkGamer if this code is running on the machine which is hosting the session. On any other machines that join this session, the host will not be local.