Add a range option to server to specify specific port client attribution

lib/TunnelAgent.js

@@ -20,6 +20,9 @@ class TunnelAgent extends Agent {
 
         // sockets we can hand out via createConnection
         this.availableSockets = [];
+        this.port = null;
+        this.clientId = options.clientId
+        this.portManager = options.portManager || null;
 
         // when a createConnection cannot return a socket, it goes into a queue
         // once a socket is available it is handed out to the next callback
@@ -63,13 +66,14 @@ class TunnelAgent extends Agent {
         });
 
         return new Promise((resolve) => {
-            server.listen(() => {
-                const port = server.address().port;
-                this.debug('tcp server listening on port: %d', port);
+            const port = this.portManager ? this.portManager.getNextAvailable(this.options.clientId) : null;
+            server.listen(port,() => {
+                this.port = server.address().port
+                this.debug('tcp server listening on port: %d (%s)', this.port, this.clientId);
 
                 resolve({
                     // port for lt client tcp connections
-                    port: port,
+                    port: this.port,
                 });
             });
         });
@@ -115,6 +119,9 @@ class TunnelAgent extends Agent {
         socket.once('error', (err) => {
             // we do not log these errors, sessions can drop from clients for many reasons
             // these are not actionable errors for our server
+            if(this.portManager){
+                this.portManager.release(this.port);
+            }
             socket.destroy();
         });