NetworkManager Error: Server client disconnect error: 1

Nikolat93 · Jan 1, 2019

Fattie said: ↑

Just for anyone googling here, perhaps new to Unity networking .....

Unity give you as a built-in a NetworkManager. However it ....... doesn't work.

This is hugely typical of Unity / Unity documentation.

In the examples and so on, it will say things like "Just add a NetworkManager !"

In simple reality though, it literally doesn't work at all.

1. You very simply, cannot, use the supplied NetworkManager. It's that simple.

2. There are (at least) four functions which you must provide (that is to say, override in c#) to get a basic demo working.

See example listing below.

Note that this is only the most basic example to actually "make it work in a demo". You face many, many problems.

Just one notable issue is that - surprise ! - Unet does not by default eliminate the abstract player items (i.e. the spawned prefabs) of a thing when it disconnects. In some game milieu, you do want that behavior, but it's surprising that it is the unmentioned default. The function NetworkServer.DestroyPlayersForConnection destroys - that is to say on every client still connected - two things, the abstract player item of the lost player, and, any/all authority objects which the lost player had previously, during the game, had created (ie, as described in this post at Section 4, Example 2. {Note that, if indeed it IS the nature of your game that you DO want to keep the 'ghost' player in there, that involves considerable work as to tracking it and perhaps allowing the same actual human to re-take control of it, if/when that human again connects.}

Also in particular see the posts of @Homicide / Obiwan above for more useful info.

So who disconnected?

In any real-world scenario, when there's a disconnect, you'll need to of course know "which thing" or "which user" disconnected.You simply cannot do networking without this, but it is NOT, repeat NOT built-in to unet in any way. You have to program this completely manually from scratch.There is a general example of that at the bottom, see below.

Functions poorly named ...

(In Unity ? No, really?)

"OnServerDisconnect" means "here on the server, we have learned that someone has disconnected"

and

"OnClientDisconnect" means "here on one of the clients, we have learned that the server has disappeared"

You may ask

But why does it just crash?

There's a rational reason - in c# you can not enforce an abstract-like override need. This is an everyday feature of the language. (You can see endless discussion of this, example ) It's quite normal in such cases to just "force the program to crash". IE, if your colleagues have forgotten the override, we know it simply and literally won't work without the override (you must provide the function in question, or the app just doesn't work), so it's perfectly reasonable to "just crash". In that way, during development, your colleagues know what's going on. So that's what's happening here.

But.

If Unity had simply added in the error text "You must override OnClientDisconnect" then none of this massive problem would ever have arisen.

That is what you do on any team when you force a crash because of a missing function that must be written as an override. You just have a 3-word message for your colleagues ... "you forgot BlendRobotArm". It's a basic.

The thousands of words of garbage doco and examples on Unity networking could all be replaced with the short sentence "BTW, NetworkBehaviour doesn't work, you must write your own code for these four functions ..."

That's ALL that is needed to know. :/

Code samples....

Code (CSharp):

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.Networking;

public class OurNetworkManager : NetworkManager {

public override void OnServerConnect(NetworkConnection nc) {

base.OnServerConnect(nc);

int cid = nc.connectionId;

int hid = nc.hostId;

LogDisplay.Log("server: on server connect " + cid + " " + hid);

}

public override void OnClientConnect(NetworkConnection nc) {

base.OnClientConnect(nc);

// ** critical ** you must stop your client discovery RIGHT HERE,

// directly after the call to the base. you actually can NOT do it

// in your discovery client

int cid = nc.connectionId;

int hid = nc.hostId;

LogDisplay.Log("client! on client connect " + cid + " " + hid);

}

public override void OnClientDisconnect(NetworkConnection nc) {

Log .. this means HERE ON A CLIENT, the server has disappeared

// 1. You certainly want to do this:

StopClient();

// 2. Almost certainly, you will seek a new server ...

// using your own code, you will basically again launch your DiscoveryClient

}

public override void OnServerDisconnect(NetworkConnection nc) {

Log .. this means, HERE ON THE SERVER, one of our clients has disappeared

// 1. you will absolutely have to keep track of your connections

Grid.SetToNull(nc);

// 2. it is usually absolutely essential to do this ...

// (if you do wish to keep a 'ghost' player going, that is far more difficult)

NetworkServer.DestroyPlayersForConnection(nc);

}

}

(
Important aside:

(ONE) For late 2018, you must stop your client discovery as shown above in the network manager in OnClientConnect, specifically directly after the call to the base. You actually can NOT do it in the discovery client as you would assume.

(TWO) AND there is a racetrack bug in Unity which allows the discoverer to be called more than once even when you turn it off; you have to manually add a lock boolean: see discovery client script below.
)

Continuing .. How do you know "which" thing disconnected?

You must anyway have some sort of (say) singleton which keeps track of your connections.

As each thing connects, you must save somewhere that connection so you know who is who. (Notice "connection_OC1" etc below.)

You may well ask, how does each new connecting client identify itself to the server? That's entirely up to you. (A great example of something that is totally non-optional - you Must Do It - but, surprise, it's not in Unet.) Here's an example in a static, LAN, case of something like that .. ("OurNet" is our own standard base typical networking material.)

Code (CSharp):

public void OurNetIdentifySelfToServer() {

CmdOurNetIdentifySelfToServer( Hardware.whatAmIText );

}

[Command]

void CmdOurNetIdentifySelfToServer(string connectingClientIdString) {

LogDisplay.Log("on server .. OurNetIdentifySelfToServer .. >" + connectingClientIdString + "<");

if (connectingClientIdString == "oculus 1") { Grid.connection_OC1 = connectionToClient; }

.. etc

.. etc

You would (must) call "OurNetIdentifySelfToServer" in "OnStartLocalPlayer()" in your NetworkBehavior.

Again, and this is very confusing to new networkers, it's utterly "up to you" to do this (absolutely basic, essential) thing of "keeping track of all the connections and being able to identify which is which."

When something disconnects, use a routine something like "Describe" below to look up which one it was. (You may well have a hash, array, or whatever, this example was a fixed LAN case.)

Code (CSharp):

using UnityEngine;

using UnityEngine.Networking;

static class Grid {

// for networking ..

public static Comms commsLocalPlayer;

public static Comms commsTheServer;

public static NetworkConnection connection_OC1;

public static NetworkConnection connection_OC2;

public static NetworkConnection connection_OC3;

public static NetworkConnection connection_OC4;

public static NetworkConnection connection_OC5;

public static NetworkConnection connection_OC6;

public static NetworkConnection connection_UserKiosk;

public static string Describe(NetworkConnection nc) {

if (nc == connection_OC1) return "oc1";

if (nc == connection_OC2) return "oc2";

if (nc == connection_OC3) return "oc3";

if (nc == connection_OC4) return "oc4";

if (nc == connection_OC5) return "oc5";

if (nc == connection_OC6) return "oc6";

if (nc == connection_UserKiosk) return "oc6userKiosk";

return "??UNKNOWN NETWORK CONNECTION??";

}

// you definitely need to be able to un-set these, when, something disconnects

public static string SetToNull(NetworkConnection nc) {

if (nc == connection_OC1) connection_OC1 = null;

if (nc == connection_OC2) connection_OC2 = null;

if (nc == connection_OC3) connection_OC3 = null;

if (nc == connection_OC4) connection_OC4 = null;

if (nc == connection_OC5) connection_OC5 = null;

if (nc == connection_OC6) connection_OC6 = null;

if (nc == connection_UserKiosk) connection_UserKiosk = null;

return "??UNKNOWN NETWORK CONNECTION?? in SetToNull";

}

...

And here then is the matching client discovery, which works perfectly with the network manager above.

Code (CSharp):

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.Networking;

public class NetworkDiscoveryClient: NetworkDiscovery {

// in the case of client discovery, there's a unity bug (late 2018)

// where on some hardware, OnReceivedBroadcast will be called more

// than once even if you "stop" the discoverer.

// so you have to do this:

bool hasRecievedBroadcastAtLeastOnce = true;

void Awake() {

// it's extremely likely you will have to keep track of this

// both game object and component, in some global location

Grid.theNetworkDiscoveryGameObject = gameObject;

Grid.theNetworkDiscoveryClient = this;

}

// a network discovery custom script can be either a client or a server

// to make it one or the other, simply call "startAs .." on launch or relaunch

// you often have to "turn on again" a discovery process (ie, when the server

// disappears and you want to start looking for a server again)

// hence you must use OnEnable rather that Awake or Start

protected void OnEnable() {

if (.. during development, you want to use 'localhost' ..) {

OnReceivedBroadcast("localhost", "");

return;

}

Initialize();

hasRecievedBroadcastAtLeastOnce = false; // must do this precisely here

StartAsClient();

}

public override void OnReceivedBroadcast(string fromAddress, string data) {

// deal with Unity bug, see notes above

if (hasRecievedBroadcastAtLeastOnce) {

YourLog("+++ avoided Unity racetrack bug, cool eh? would have crashed otherwise");

return;

}

hasRecievedBroadcastAtLeastOnce = true;

YourLog("in client discovery. found server .. fromAddress");

// you now want to turn off discovery

// (as needed, it will get turned on again in YourNetworkManager#OnClientDisconnect)

// intriguingly you CAN NOT DO IT HERE ... due to yet another Unity bug

// you must do it in YourNetworkManager#OnClientConnect IMMEDIATELY after base.

// see the notes in red in this forum post up above

// StopBroadcast(); .. can not do this here

NetworkManager networkManager = Object.FindObjectOfType<NetworkManager>();

if (networkManager == null) { .. you forgot the network manager .. return; }

// to start the client, simply do these two things:

networkManager.networkAddress = fromAddress;

networkManager.StartClient();

gameObject.SetActive(false);

// if the server disappears, you'll start discovery again simply

// by re-enabling this gameobject

}

}

Here is the matching NetworkDiscoveryServer

Code (CSharp):

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using UnityEngine.Networking;

public class NetworkDiscoveryServer: NetworkDiscovery

{

void Start() { // become a discovery-server

// a network discovery custom script can be either a client or a server

// to make it one or the other, simply use the "StartAs .." call inside the

// ordinary MonoBehavior "Start" call.

NetworkManager networkManager = Object.FindObjectOfType<NetworkManager>();

if (networkManager == null) {

LogDisplay.Log("BAD SET UP - you totally forgot a NetworkManager");

return;

}

///networkManager.StartServer();

networkManager.StartHost();

if (Grid.developmentUseLocalhost) {

LogDisplay.Log("dev .. localhost style server, no discovery");

return;

}

Initialize();

StartAsServer();

LogDisplay.Log("as server .. start discovery");

}

}

Click to expand...

Forget all this nerd S*** and pointless singletons. You just need to give a little bit of a buffer before you call stop host.
*NOTE* this is specifically for the host id out of bounds error on disconnects.

public override void OnServerDisconnect(NetworkConnection conn)
{
NetworkServer.DestroyPlayersForConnection(conn);
StartCoroutine(StopNextFrame());
}

private IEnumerator StopNextFrame()
{
yield return null;
StopHost();
}

Fattie · Dec 31, 2018

Ahh .. @Nikolat93

were you referring to this:

>You must anyway have some sort of (say) singleton which keeps track of your connections.
Click to expand...

You in fact must, absolutely must, have something that keeps track of connections - as it says "anyway". Like, you won't be able to do multiplayer gaming unless you do that. Somewhat bizarrely, Unity does not bother to "do that built-in" so you have to do it yourself - one way or another.

i.e., unrelated to the specific issue discussed here, you have to do that anyways.

(You certainly don't have to use a singleton - use any technique you want. On every project I've ever been on, it's just been an ordinary old singleton, though.)

Hppy new year all !

Nikolat93 · Jan 1, 2019

Fattie said: ↑

Ahh .. @Nikolat93

were you referring to this:

You in fact must, absolutely must, have something that keeps track of connections - as it says "anyway". Like, you won't be able to do multiplayer gaming unless you do that. Somewhat bizarrely, Unity does not bother to "do that built-in" so you have to do it yourself - one way or another.

i.e., unrelated to the specific issue discussed here, you have to do that anyways.

(You certainly don't have to use a singleton - use any technique you want. On every project I've ever been on, it's just been an ordinary old singleton, though.)

Hppy new year all !
Click to expand...

Sorry i wasn't trying to create any confusion or knock your singleton, I was just saying that it's possible to resolve the host id out of bounds error without creating a bunch of extra code. Thanks very much for your informative post and pushing me in the right direction (to avoid the racetrack condition with unet static update).

This is specifically for my game where when one player exits the match I want the other player to be disconnected. Push the stophost() call to the next frame (when called from host side) and voila, no out of bounds error. You are correct that OnServerConnect and OnClientConnect need to be overriden.

I tried to strip my code just to share the essential, but left a typo in the process. It is fixed now.

Thank you for sharing your research, and happy new year!

Moitroid · Jan 19, 2019

@Fattie in NetworkDiscoveryClient.OnEnable (line 31 of your NetworkDiscoveryClient code specifically), it says to use localhost during development. But what about after development is done?

Fattie · Jan 21, 2019

hi @Moitroid , very simple !

say you have a global variable "developmentOnly"

IF "developmentOnly" is true, you simply execiute that block of code .....

... note at the end of that block of code it "return"s.

in the normal ordinary situation ("developmentOnly" is false), the computer will simply ignore that piece of code. And then the rest of the code below, does all the work for you, in the normal case!

All the "normal" code, is, simply, the code below that block.

That's all there is to it! it's just "breakaway" code structure.

Here's an example of if-else code structure:

{
if (X)
do something
else
do something else
}

Here's an example of "breakaway" code structure:

{
if (some unusual case)
{
do something
return
}
have all the normal code here
have all the normal code here
have all the normal code here
}

if the second part (the "normal part") is very long, many people use "breakaway" as in the second example. This is common in all languages.

(Again, it means nothing: it's just code format. You could format it like the upper code example here "if-else", if you preferred.)

Hope that all makes sense. Don't hesitate to ask anything.

Moitroid · Jan 22, 2019

Thank you very much @Fattie

What about the ip address to use? I know we use localhost for development, but what ip and port is recommended when done with development?

Giantbean · Jun 1, 2020

Years later I would like to revisit this post and perhaps perform a bit of necromancy as the need for networking is far from dead even if UNet has been depreciated. So I ask is Fattie's solution still relevant? Is there a better method in Unity 2019.3+ or the upcoming 2020.+ I would also ask if things change based on mobile deployment or a VR game. Lastly how does the development or production use of local host vary if you will only ever connect by a LAN cable and network switch and never over the web?

Fattie · Jun 1, 2020

@Giantbean - I actually don't know either!

Unity were "about to" release their totally new networking.

When they do that, all of this would be historic information of no value.

BUT I actually have no clue if they have done that yet! As I have not started up a Unity project for a few months, so I'm not up-to-the-minute. Someone else will have to answer!

* Regarding your question about LAN-only. You would need to start a separate thread for that different issue. Funnily enough we did indeed do a LAN-only project, and it's tricky. I think I made a post on here explaining the issues. IN any event it's a separate good question. Cheers!

Giantbean · Jun 1, 2020

Thanks Fattie.

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NetworkManager Error: Server client disconnect error: 1