IMessageHandler onMessage return?

[Kwibble]

Say I have a message that gets sent to the server:

MessageServerRandomStuff

I can send this message and handle it in:

@Override
public IMessage onMessage(MessageServerRequestGuiOpen message, MessageContext ctx)
{
return null;
}

 

What I am wanting to know is this: Can I send another message to the server as the returned message? Or does it have to be a client received message in the return? (And vice versa for server sending to client).

[Kwibble]

The reason I asked was to see if I could make s generic GUI button pressed message and from there call the normal playerinfo (IExtendedEntityProperties) message. Now I guess I am going to have to make a new message for every GUI button press that does something special server wise?