Does bitcoind send message headers and payload separately in P2P protocol? I am connecting to my local bitcoind using TCP and observed the following behavior: 

I see many messages where only header is given or only part of the payload is attached. Of course, it could be a bug my code too. 

Are the bytes sent in chunks? Which of the following are valid?

|header1|payload1|     (as per documentation, this is valid)
|header1|              (no payload, even though required. Have seen this)
|payload1|             (no header, have seen this)
|header1|partPayload1| (incomplete payload, not sure if seen these)
|partPayload1|         (part earlier header's payload, not sure if seen these)
|header1|payload1|header2|payload2| 
|header1|payload1|header2|partPayload2|  
|header1|partPayload1|header2|
|partPayload1|header2|payload2|


Note: I am using version number 70002, relay = 1 and services = 0.

EDIT: Generally I wait for the remaining bytes, and most of the times they arrive, but in rare cases, around 2%, some other header arrives. This happens only with tx messages. 

EDIT2: Based on the comments below, it seems likely that there is a bug in my code. I'll check and revert. 

EDIT3: Was a bug in my code. I was assuming that partial data packets correspond to a single header. There can be multiple headers after the data is complete (in the same packet). This makes sense once I consider it as a stream.
TCP is a stream protocol. Even though on the wire the stream is submitted as a series of IP messages, semantically it is just a stream of bytes.

This means that at the application level you shouldn't care about the message boundaries. Routers and other internet infrastructure can arbitrarily split up data into packets to fit in their underlying protocols (e.g. Ethernet has frames of at most 1500 bytes).