From Garry's Mod
Sends the current message to the server.
Sends a simple "hello_world" message with the string "Hi" to the server
net.Start( "hello_world" ) net.WriteString( "Hi" ) net.SendToServer()
The netmessage "hello_world" is sent to the server. The server can handle this with net.Receive. Remember that any client has the potential to send any net message at any time. On your server-side net.Receive, make sure to verify the message sender's permissions whenever you can and prevent expensive functions from being run too often.