Class: stream.Writable
The Writable stream interface is an abstraction for a destination that you are writing data to. 
Examples of writable streams include: 
HTTP requests, on the client HTTP responses, on the server fs write streams zlib streams crypto streams TCP sockets child process stdin 
process.stdout, process.stderr
 
Event: 'drain'
If a stream.write(chunk) call returns false, then the 'drain' event will indicate when it is appropriate to begin writing more data to the stream. 
// Wri