Question: As part of strengthening session authentication security for a site that I am building, I am trying to compile a list of the best ways to register a user's computer as a second tier of validation - that is in addition to the standard username/password login, of course. Typical ways of registering a user's computer are by setting a cookie and or IP address validation. As prevalent as mobile computing is, IP mapping is less and less a reliable identifier. Security settings and internet security & system optimization software can make it difficult to keep a cookie in place for very long. 

Are there any other methods that can be used for establishing a more reliable computer registration that doesn't require the user to add exceptions to the various cookie deleting software?

Answer: 
Simply calling read doesn't guarantee that you will receive all the 63 bytes or that you receive the 63 bytes you were hoping for.. I would suggest that you somehow determine how much data you need to receive(send the data length first) and then put the recv function in a loop until you have all the data.. The send function(from the client) should be checked also.
How about trying to close the socket at the end of dostuff()?
The server may be getting too many open connections.