serve command exiting when web socket port is already in use (#1179)

* Handled web socket port used issue

* Lint

src/cmd/serve.rs

@@ -326,10 +326,17 @@ pub fn serve(
             }
         })
         .unwrap();
+
         let broadcaster = ws_server.broadcaster();
+
+        let ws_server = ws_server
+            .bind(&*ws_address)
+            .map_err(|_| format!("Address {} is already in use.", &ws_address))?;
+
         thread::spawn(move || {
-            ws_server.listen(&*ws_address).unwrap();
+            ws_server.run().unwrap();
         });
+
         Some(broadcaster)
     } else {
         println!("Watching in watch only mode, no web server will be started");