Disconnect all mobile clients when all UI clients leave

Summary: Context https://fb.workplace.com/groups/flippersupport/permalink/1730762380737746/

Reviewed By: lblasa

Differential Revision: D51510348

fbshipit-source-id: afafcdd6b89bf1038fec65a7c3e8c2dd9cfd0768

desktop/flipper-server-core/src/app-connectivity/BrowserServerWebSocket.tsx

@@ -148,6 +148,10 @@ class BrowserServerWebSocket extends SecureServerWebSocket {
 
   protected verifyClient(): ws.VerifyClientCallbackSync {
     return (info: {origin: string; req: IncomingMessage; secure: boolean}) => {
+      if (!this.acceptingNewConections) {
+        return false;
+      }
+
       if (isFBBuild) {
         try {
           const urlObj = new URL(info.origin);

desktop/flipper-server-core/src/app-connectivity/ServerRSocket.tsx

@@ -293,6 +293,11 @@ class ServerRSocket extends ServerWebSocketBase {
       },
     };
   };
+
+  protected stopAcceptingNewConectionsImpl(): void {
+    // Did not find a straightforard way to iterate through RSocket open connections and close them.
+    // We probably should not care and invest in it anyway as we are going to remove RScokets.
+  }
 }
 
 export default ServerRSocket;

desktop/flipper-server-core/src/app-connectivity/ServerWebSocket.tsx

@@ -294,11 +294,20 @@ class ServerWebSocket extends ServerWebSocketBase {
    */
   protected verifyClient(): VerifyClientCallbackSync {
     return (_info: {origin: string; req: IncomingMessage; secure: boolean}) => {
+      if (!this.acceptingNewConections) {
+        return false;
+      }
       // Client verification is not necessary. The connected client has
       // already been verified using its certificate signed by the server.
       return true;
     };
   }
+
+  protected stopAcceptingNewConectionsImpl(): void {
+    this.wsServer?.clients.forEach((client) =>
+      client.close(WSCloseCode.GoingAway),
+    );
+  }
 }
 
 export default ServerWebSocket;

desktop/flipper-server-core/src/app-connectivity/ServerWebSocketBase.tsx

@@ -15,6 +15,7 @@ import {
   SignCertificateMessage,
 } from 'flipper-common';
 import {SecureServerConfig} from './certificate-exchange/certificate-utils';
+import GK from '../fb-stubs/GK';
 
 /**
  * Defines an interface for events triggered by a running server interacting
@@ -98,6 +99,8 @@ export interface ServerEventsListener {
  * RSocket, WebSocket, etc.
  */
 abstract class ServerWebSocketBase {
+  protected acceptingNewConections = true;
+
   constructor(protected listener: ServerEventsListener) {}
 
   /**
@@ -169,6 +172,23 @@ abstract class ServerWebSocketBase {
 
     return undefined;
   }
+
+  startAcceptingNewConections() {
+    if (!GK.get('flipper_disconnect_device_when_ui_offline')) {
+      return;
+    }
+    this.acceptingNewConections = true;
+  }
+
+  stopAcceptingNewConections() {
+    if (!GK.get('flipper_disconnect_device_when_ui_offline')) {
+      return;
+    }
+    this.acceptingNewConections = false;
+    this.stopAcceptingNewConectionsImpl();
+  }
+
+  protected abstract stopAcceptingNewConectionsImpl(): void;
 }
 
 export default ServerWebSocketBase;