added option to specify port range for client ports

lib/TunnelAgent.js

@@ -4,8 +4,12 @@ import assert from 'assert';
 import log from 'book';
 import Debug from 'debug';
 
+import { getPort } from 'portfinder';
 const DEFAULT_MAX_SOCKETS = 10;
 
+const DEFAULT_MIN_PORT_RANGE = 1024;
+const DEFAULT_MAX_PORT_RANGE = 65535;
+
 // Implements an http.Agent interface to a pool of tunnel sockets
 // A tunnel socket is a connection _from_ a client that will
 // service http requests. This agent is usable wherever one can use an http.Agent
@@ -31,6 +35,9 @@ class TunnelAgent extends Agent {
         this.connectedSockets = 0;
         this.maxTcpSockets = options.maxTcpSockets || DEFAULT_MAX_SOCKETS;
 
+        this.client_min_port_range = options.client_min_port_range || DEFAULT_MIN_PORT_RANGE;
+        this.client_max_port_range = options.client_max_port_range || DEFAULT_MAX_PORT_RANGE;
+
         // new tcp server to service requests for this client
         this.server = net.createServer();
 
@@ -63,14 +70,19 @@ class TunnelAgent extends Agent {
         });
 
         return new Promise((resolve) => {
-            server.listen(() => {
-                const port = server.address().port;
-                this.debug('tcp server listening on port: %d', port);
+            getPort({
+              port: this.client_min_port_range,    // minimum port
+              stopPort: this.client_max_port_range // maximum port
+            }, (err,port) => {
+              server.listen(port,() => {
+                  const port = server.address().port;
+                  this.debug('tcp server listening on port: %d', port);
 
-                resolve({
-                    // port for lt client tcp connections
-                    port: port,
-                });
+                  resolve({
+                      // port for lt client tcp connections
+                      port: port,
+                  });
+              });
             });
         });
     }