why this is error?

[daktem21]

server : send 3 bytes first, and send another 9 bytes

client : recv 12 bytes at a time

why error?

[MikeAThon]

Not an error. That's the way TCP is designed to work.

TCP is a streaming protocol, not a message protocol. As far as TCP is concerned, it's sending and receiving a stream of bytes. It's the responsibility of your application (not of TCP) to determine what the bytes mean.

If you are trying to implement a messaging protocol, then one simple solution is to preface each send() with the number of bytes being sent in the message. Then the recipient can figure out how many bytes are in the message, even though more than one message (or only a partial message) is received.

Mike

[dog_pig_baby]

It is simple to use setsockopt to close the Nagle arithmetic


or like what MikeAThon says that is in common use

[MikeAThon]

Turning Nagle off will not affect the basic behavior of TCP. It's still a streaming protocol, and will group the bytes independently of your attempts to control groupings through careful calls to send(), regardless of whether Nagle is turned on or off.

Mike