To switch Android compatible socket.io library.
Other computers now able to connect to ws webserver (http://49.128.39.190:8887) after doing public IP port mapping to internal ip for big Mac (192.168.1.113:8887).
However, Android was still unable to connect to webserver despite successfully compiling and running two different Android WebSocket libraries (Java-WebSocket and AutobahnAndroid).
This was likely due to the fact that socket.io has an additional handshake on top of WebSocket protocol, hence only Android (compatible) library for socket.io (not just WebSocket) should be used for Android.
Ref: http://nkzawa.tumblr.com/post/46850605422/connecting-to-a-socket-io-server-from-android
After much online searching (esp. on stackoverflow), it seemed the most popular choice is socket.io-java-client by Gottox at:
https://github.com/Gottox/socket.io-java-client
To try out socket.io-java-client.