Java idiom
You don't need this method (sort of working like a getter) - you can just use self.open everywhere you would use self.open().
docstrings
Parse argv first
This might just be my personal taste, but I like to do command line argument parsing before I execute any other code.
Increase allowable backlog
listen(n) allows up to n clients to queue waiting for the listen socket to connect.  You might as well set it higher.  (5 is the maximum allowable.)
Changing use of rcvr.is_open() to rcvr.open
Goes with the previous change
Avoid namespace collisions
I tend to avoid using the name of a module as the name of an object attribute or a variable.  Your code here works fine, but if you changed your mind and decided you wanted to `import socket` in this file, you've overwritten the name socket in this scope, which could be bad.
change variable name from "data"
More specific naming!
oops, fixing socket -> sock here too