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type - message type, 1 to 99 (higher values are reserved for the system) msg$ - the message text to send from_player - id of the sending player (one of your local players) to_player (optional) - id of the player to send to; 0 broadcasts to every player (default) reliable (optional) - 1 guarantees delivery (default); 0 is faster but the message may be lost |
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Sends a message to one player, or to everyone, in the current network game. Returns 1 if the message was handed to the network, 0 on failure. The receiving machines pick it up with RecvNetMsg and read it back through NetMsgType, NetMsgFrom, NetMsgTo and NetMsgData$. The type is your own protocol: pick numbers 1-99 and give them meanings (1 = chat, 2 = position update, 3 = fire...). Values from 100 up belong to the system messages RecvNetMsg reports. To keep traffic down, pack related values into one string - "x,y,frame" - rather than sending three messages. Reliable messages always arrive but cost more; for things sent every frame where a lost one does not matter (positions), send unreliable and let the next update cover any gap. One big gotcha: messages between two players on the same machine are never delivered - RecvNetMsg only sees messages from other machines. So a player does not hear their own broadcasts, and testing needs two copies of the program running (they can share one PC via a loopback join). See also: RecvNetMsg, NetMsgType, NetMsgData, CreateNetPlayer. |
; SendNetMsg Example
; ------------------
; Run TWO copies of this program on one machine: the first copy
; hosts "demo game", the second finds it over loopback and joins.
; The copies then greet each other with SendNetMsg.
SeedRnd MilliSecs()
; Join an existing demo game if one is running, else host one
status=JoinNetGame("demo game","127.0.0.1")
If status=1 Then
Print "Joined an existing demo game as a client"
Else
If HostNetGame("demo game")=2 Then status=2
If status=2 Then Print "No game found - hosting a new demo game"
EndIf
If status=0 Then
Print "Could not host or join a network game."
Else
; A player must exist before messages can be sent or received
me=CreateNetPlayer("Player"+Rand(100,999))
Print "Playing as '"+NetPlayerName$(me)+"'"
; SendNetMsg type,data$,from,to,reliable
; type 1-99 = your own message kinds (here 1 = greeting)
; to 0 = broadcast to every player in the game
; reliable = 1 guarantees delivery
SendNetMsg 1,"Hello from "+NetPlayerName$(me),me,0,1
Print "Broadcast a greeting with SendNetMsg"
; Listen for the other copy for 6 seconds
Print "Listening for messages for 6 seconds..."
start=MilliSecs()
heard=0
While MilliSecs()-start<6000
If RecvNetMsg() Then
mtype=NetMsgType()
If mtype>=1 And mtype<=99 Then
heard=heard+1
Print "Received '"+NetMsgData$()+"' from "+NetPlayerName$(NetMsgFrom())
; Answer greetings directly to their sender
If mtype=1 Then SendNetMsg 2,"Nice to meet you!",me,NetMsgFrom(),1
EndIf
If mtype=100 Then Print NetPlayerName$(NetMsgFrom())+" joined the game"
EndIf
Delay 10
Wend
If heard=0 Then
Print "No messages arrived - a program only hears OTHER copies."
Print "Start a second copy of this example to see the exchange."
EndIf
StopNetGame
Print "Left the game"
EndIf
Print ""
Print "Press any key to close the example"
WaitKey
End