# EventService

> The EventService is a singleton implementation of a ChannelClient that runs on all instances of Unity. It is connected to the "events" channel and allows a Unity instance to send JSON messages to other EventService s in external process, or other instances of Unity.

## Definition

* **Type:** Class
* **Namespace:** [UnityEditor.MPE](/engine/6000.5/script-reference/unityeditor/mpe.md)
* **Assembly:** UnityEditor.CoreModule

```csharp
public static class EventService
```

## Remarks

The [EventService](/engine/6000.5/script-reference/unityeditor/mpe/eventservice.md) can send fire-and-forget messages (see [EventService.Emit](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/emit.md)), or request information or from a single client (see [EventService.Request](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/request.md)).

## Examples

```csharp
using UnityEditor;
using UnityEngine;
using UnityEditor.MPE;
using System;

public static class EventServiceDocExample
{
    static Action s_CustomLogEventDisconnect;
    static Action s_PingPongEventDisconnect;

    [MenuItem("EventServiceDoc/Step 0")]
    static void StartChannelService()
    {
        if (!ChannelService.IsRunning())
        {
            ChannelService.Start();
        }
        Debug.Log($"[Step 0] ChannelService Running: {ChannelService.GetAddress()}:{ChannelService.GetPort()}");
    }

    [MenuItem("EventServiceDoc/Step 1")]
    static void SetupEventServiceHandlers()
    {
        Debug.Log("[Step 1] Setup handlers");
        s_CustomLogEventDisconnect = EventService.RegisterEventHandler("custom_log", (eventType, args) => {
            Debug.Log($"Log a {eventType} {args[0]}");
        });

        s_PingPongEventDisconnect = EventService.RegisterEventHandler("pingpong", (eventType, args) =>
        {
            Debug.Log($"Receive a {eventType} {args[0]}");
            return "pong!";
        });
    }

    [MenuItem("EventServiceDoc/Step 2")]
    static void EmitMessage()
    {
        Debug.Log("[Step 2] Emitting a custom log");
        EventService.Emit("custom_log", "Hello world!", -1, EventDataSerialization.JsonUtility);
    }

    [MenuItem("EventServiceDoc/Step 3")]
    static void SendRequest()
    {
        Debug.Log("[Step 3] Sending a request");
        EventService.Request("pingpong", (err, data) =>
        {
            Debug.Log($"Request fulfilled: {data[0]}");
        },
            "ping", -1, EventDataSerialization.JsonUtility);
    }

    [MenuItem("EventServiceDoc/Step 4")]
    static void CloseHandlers()
    {
        Debug.Log("[Step 4] Closing all Event handlers");
        s_CustomLogEventDisconnect();
        s_PingPongEventDisconnect();
    }
}

/*

When you execute the five menu items one after the other, Unity prints the following messages to the Console window:

[Step 0] ChannelService Running: 127.0.0.1:65000

[Step 1] Setup handlers

[Step 2] Emitting a custom log

Log a custom_log Hello world!

[Step 3] Sending a request

Receive a pingpong ping

Request fulfilled: pong!

[Step 4] Closing all Event handlers

*/
```

## Static Properties

| Property                                                                                   | Description                                                                                                                               |
| ------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------- |
| [isConnected](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/isconnected.md) | The EventService connected to the [ChannelService](/engine/6000.5/script-reference/unityeditor/mpe/channelservice.md)'s "events" channel. |

## Static Methods

| Method                                                                                                           | Description                                                                                                                                                                                                                                                                                                                                  |
| ---------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [CancelRequest](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/cancelrequest.md)                   | Checks whether there is a pending request for a specific event and, if there is, cancels it. See [EventService.Request](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/request.md) for more details on Request.                                                                                                                |
| [Clear](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/clear.md)                                   | Clear all pending Requests.                                                                                                                                                                                                                                                                                                                  |
| [Close](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/close.md)                                   | Closes the EventService, terminates connections to the ChannelService, and ensures that no more handlers are processed.                                                                                                                                                                                                                      |
| [Emit](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/emit.md)                                     | Sends a fire-and-forget message to all [ChannelClient](/engine/6000.5/script-reference/unityeditor/mpe/channelclient.md)s connected to the "events" route.                                                                                                                                                                                   |
| [IsRequestPending](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/isrequestpending.md)             | Checks whether a request is pending on a specific event. For more information about Request, see [EventService.Request](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/request.md).                                                                                                                                            |
| [Log](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/log.md)                                       | Sends a log message to the [ChannelService](/engine/6000.5/script-reference/unityeditor/mpe/channelservice.md). Log messages are printed to the Console window.                                                                                                                                                                              |
| [RegisterEventHandler](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/registereventhandler.md)     | Registers a handler for a specific event type. The handler is called whenever a message of the specified type is sent. Messages are sent using [EventService.Emit](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/emit.md) or [EventService.Request](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/request.md). |
| [Request](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/request.md)                               | Sends a request to all connected clients on the "events" channel.                                                                                                                                                                                                                                                                            |
| [Start](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/start.md)                                   | Starts the EventService so it listens to new messages.                                                                                                                                                                                                                                                                                       |
| [Tick](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/tick.md)                                     | Ticks the [EventService](/engine/6000.5/script-reference/unityeditor/mpe/eventservice.md). This processes all incoming and outgoing messages. By default, the EventService is ticked on each [EditorApplication.update](/engine/6000.5/script-reference/unityeditor/editorapplication/update.md).                                            |
| [UnregisterEventHandler](/engine/6000.5/script-reference/unityeditor/mpe/eventservice/unregistereventhandler.md) | Unregisters a handler from a specific event.                                                                                                                                                                                                                                                                                                 |