Move port range to config. Throw exception if no free port is available within the range

app/Server/Connections/ConnectionManager.php

@@ -5,6 +5,7 @@ namespace App\Server\Connections;
 use App\Contracts\ConnectionManager as ConnectionManagerContract;
 use App\Contracts\SubdomainGenerator;
 use App\Http\QueryParameters;
+use App\Server\Exceptions\NoFreePortAvailable;
 use Ratchet\ConnectionInterface;
 use React\EventLoop\LoopInterface;
 use React\Socket\Server;
@@ -82,8 +83,10 @@ class ConnectionManager implements ConnectionManagerContract
 
     protected function getSharedTcpServer(): Server
     {
-        $portRange = [50000, 62000];
+        $portRange = config('expose.admin.tcp_port_range');
-        $port = $portRange[0];
+
+        $port = $portRange['from'] ?? 50000;
+        $maxPort = $portRange['to'] ?? 60000;
 
         do {
             try {
@@ -92,6 +95,10 @@ class ConnectionManager implements ConnectionManagerContract
             } catch (\RuntimeException $exception) {
                 $portFound = false;
                 $port++;
+
+                if ($port > $maxPort) {
+                    throw new NoFreePortAvailable();
+                }
             }
         } while (! $portFound);
 

app/Server/Exceptions/NoFreePortAvailable.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace App\Server\Exceptions;
+
+class NoFreePortAvailable extends \Exception
+{
+
+}

app/Server/Http/Controllers/ControlMessageController.php

@@ -5,6 +5,7 @@ namespace App\Server\Http\Controllers;
 use App\Contracts\ConnectionManager;
 use App\Contracts\UserRepository;
 use App\Http\QueryParameters;
+use App\Server\Exceptions\NoFreePortAvailable;
 use Ratchet\ConnectionInterface;
 use Ratchet\WebSocket\MessageComponentInterface;
 use React\Promise\Deferred;
@@ -119,7 +120,18 @@ class ControlMessageController implements MessageComponentInterface
 
     protected function handleTcpConnection(ConnectionInterface $connection, $data, $user = null)
     {
-        $connectionInfo = $this->connectionManager->storeTcpConnection($data->port, $connection);
+        try {
+            $connectionInfo = $this->connectionManager->storeTcpConnection($data->port, $connection);
+        } catch (NoFreePortAvailable $exception) {
+            $connection->send(json_encode([
+                'event' => 'authenticationFailed',
+                'data' => [
+                    'message' => config('expose.admin.messages.no_free_tcp_port_available'),
+                ],
+            ]));
+            $connection->close();
+            return;
+        }
 
         $connection->send(json_encode([
             'event' => 'authenticated',

config/expose.php

@@ -151,6 +151,24 @@ return [
         */
         'validate_auth_tokens' => false,
 
+        /*
+        |--------------------------------------------------------------------------
+        | TCP Port Range
+        |--------------------------------------------------------------------------
+        |
+        | Expose allows you to also share TCP ports, for example when sharing your
+        | local SSH server with the public. This setting allows you to define the
+        | port range that Expose will use to assign new ports to the users.
+        |
+        | Note: Do not use port ranges below 1024, as it might require root
+        | privileges to assign these ports.
+        |
+        */
+        'tcp_port_range' => [
+            'from' => 50000,
+            'to' => 50003
+        ],
+
         /*
         |--------------------------------------------------------------------------
         | Maximum connection length
@@ -232,6 +250,8 @@ return [
             'subdomain_taken' => 'The chosen subdomain :subdomain is already taken. Please choose a different subdomain.',
 
             'custom_subdomain_unauthorized' => 'You are not allowed to specify custom subdomains. Please upgrade to Expose Pro.',
+
+            'no_free_tcp_port_available' => 'There are no free TCP ports available on this server. Please try again later.'
         ],
     ],
 ];