use pump to pipe sockets

Ensures that destination socket close or destroy also does the same for
the source socket.

lib/ClientManager.js

@@ -20,6 +20,8 @@ class ClientManager {
         };
 
         this.debug = Debug('lt:ClientManager');
+
+        this.graceTimeout = null;
     }
 
     // create a new tunnel with `id`
@@ -36,11 +38,13 @@ class ClientManager {
 
         const maxSockets = this.opt.max_tcp_sockets;
         const agent = new TunnelAgent({
+            clientId: id,
             maxSockets: 10,
         });
 
         agent.on('online', () => {
             this.debug('client online %s', id);
+            clearTimeout(this.graceTimeout);
         });
 
         agent.on('offline', () => {
@@ -48,7 +52,11 @@ class ClientManager {
             // this period is short as the client is expected to maintain connections actively
             // if they client does not reconnect on a dropped connection they need to re-establish
             this.debug('client offline %s', id);
-            this.removeClient(id);
+
+            // client is given a grace period in which they can re-connect before they are _removed_
+            this.graceTimeout = setTimeout(() => {
+                this.removeClient(id);
+            }, 1000);
         });
 
         // TODO(roman): an agent error removes the client, the user needs to re-connect?
@@ -81,6 +89,7 @@ class ClientManager {
     }
 
     removeClient(id) {
+        this.debug('removing client: %s', id);
         const client = this.clients[id];
         if (!client) {
             return;