I am currently building a chat server (meebo style).
The architecture is something like this.
The most important part here is that host A will be deployed in embedded Linux.
I have 2 questions.
Also if you think my approach is wrong or there is a better approach please tell me how can I improve this architecture?
Note: This is NOT a high volume chat server.
If building V8/Node.js is prohibitive on the embedded platform, the next best thing would be to take the event loop and platform layer (libuv) and HTTP parser (http-parser) of Node, both written in C and use those as a starting point. These are the same libraries used to build Node.js so they are battle tested and will give you the performance characteristics you seek.
Ryan Dahl, author of Node.js, demonstrates exactly how to use libuv and http-parser to build an asynchronous web server in C.