When does socket recv recv size return

Question

From test  I concluded that in following three cases the socket recv recv size  will return    After the connection was closed  For example  the client side called socket close   or any socket error occurred  it would return empty string  Some data come  the size of data is more than recv size  Some data come  the size of data is less than recv size and no more data come after a short time  I found 0 1s would work     More details about  3    server py  while True      data   sock recv 10      print data   EOF    client1 py  sock sendall  12345   sock sendall  a    50    client2 py  sock sendall  12345   time sleep 0 1  sock sendall  a    50    When I run client1 py  the server py echos   12345aaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaa EOF   When I run client2 py  the server py echos   12345 EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF aaaaaaaaaa EOF   Are my conclusions correct  Where can I see the official description about  3

User · Answer

I think you conclusions are correct but not accurate.

As the docs indicates, socket.recv is majorly focused on the network buffers.

When socket is blocking, socket.recv will return as long as the network buffers have bytes. If bytes in the network buffers are more than socket.recv can handle, it will return the maximum number of bytes it can handle. If bytes in the network buffers are less than socket.recv can handle, it will return all the bytes in the network buffers.

User · Answer

Yes  your conclusion is correct  socket recv is a blocking call   socket recv 1024  will read at most 1024 bytes  blocking if no data is waiting to be read  If you don t read all data  an other call to socket recv won t block   socket recv will also end with an empty string if the connection is closed or there is an error   If you want a non-blocking socket  you can use the select module  a bit more complicated than just using sockets  or you can use socket setblocking   I had issues with socket setblocking in the past  but feel free to try it if you want

User · Answer

It ll have the same behavior as the underlying recv libc call see the man page for an official description of behavior  or read a more general description of the sockets api

[python] When does socket.recv(recv_size) return?

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