如何在python TCP套接字调用send（）和recv（）中做一个标记

Question

I am relatively new to sockets and very new to python. How would you go about making an endmark for python send() and recv().

I have searched all over and there is no easy tutorial. I have read the man page for recv(2) a thousand times and it ironically makes less sense to me each time I read it.

I would like to use the send() function in a server to let the client calling recv() know when the end of the send() is.

Do you use the flag argument of send?

Or do you use something like "|".join(str1, str2) and use an if statement in the client to recognize the | and parse the statement?

Answer 1

TCP is not message oriented protocol. It does not maintain message boundaries nor it does not help in other ways to achieve it. It is up-to the application to mark boundaries. Client and server can agree upon a method in exchange of data. Common method is to put in the message length in the data you send.

[2 byte message length][Actual Data of Interest]

The end which receives packets will always look for two byte length indicator. recv as much data indicated by length bytes, process them and again go to recv length bytes and so on.

Another method is that the application can mark the start and end of the message with markers. It also needs to handle cases where the markers can also be part of actual data.

[Start Indicator][Actual Data of Interest][ End Indicator]