Xuanji, Thanks for the comments on 'data' being bytes. I had just cared to add the feature information. I think that data detail should have been updated too. 

I think for your other two questions, we discussed it msg123051 - socket in py3k handles only bytes, sending string was wrong and test_urllib2 had the mistake in sending zero length strings which weren't detected.

However, let me see if we have to accommodate those "very special case" where data can be a zero length string just to accommodate the mistake it was present in the earlier version.