Python socket receive – incoming packets always have a different size

I’m using the SocketServer module for a TCP server.
I’m experiencing some issue here with the recv() function, because the incoming packets always have a different size, so if I specify recv(1024) (I tried with a bigger value, and smaller), it gets stuck after 2 or 3 requests because the packet length will be smaller (I think), and then the server gets stuck until a timeout.