Warn if can't attach to websocket port

config/initializers/socket.rb

@@ -9,6 +9,7 @@ require "lib/diaspora/websocket"
   EM.next_tick {
     Diaspora::WebSocket.initialize_channels
 
+    begin
       EventMachine::WebSocket.start(
                     :host => "0.0.0.0",
                     :port => APP_CONFIG[:socket_port],
@@ -22,5 +23,12 @@ require "lib/diaspora/websocket"
           ws.onclose { Diaspora::WebSocket.unsubscribe(ws.request['Path'].gsub('/',''), sid) }
         }
       end
+    rescue RuntimeError => e
+      if e.message =~ /no acceptor/
+        raise RuntimeError, "Could not listen on port #{APP_CONFIG[:socket_port]}, perhaps another process is already using it?"
+      else
+        raise
+      end
+    end
   }