Python sockets error TypeError a bytes-like object is required not str with send function

Question

I am trying to create a program that will open a port on the local machine and let others connect into it via netcat  My current code is   s   socket socket   host    127 0 0 1  port   12345 s bind  host  port    s listen 5  while True      c  addr   s accept       print  Got connection from   addr      c send  Thank you for connecting       c close     I am new to Python and sockets  But when I run this code it will allow me to send a netcat connection with the command   nc 127 0 0 1 12345   But then on my Python script I get the error for the c send   TypeError  a bytes-like object is required  not  str    I am basically just trying to open a port  allow netcat to connect and have a full shell on that machine

User · Accepted Answer

The reason for this error is that in Python 3, strings are Unicode, but when transmitting on the network, the data needs to be bytes instead. So... a couple of suggestions:

Suggest using c.sendall() instead of c.send() to prevent possible issues where you may not have sent the entire msg with one call (see docs).
For literals, add a 'b' for bytes string: c.sendall(b'Thank you for connecting')
For variables, you need to encode Unicode strings to byte strings (see below)

Best solution (should work w/both 2.x & 3.x):

output = 'Thank you for connecting'
c.sendall(output.encode('utf-8'))

Epilogue/background: this isn't an issue in Python 2 because strings are bytes strings already -- your OP code would work perfectly in that environment. Unicode strings were added to Python in releases 1.6 & 2.0 but took a back seat until 3.0 when they became the default string type. Also see this similar question as well as this one.

User · Answer

You can decode it to str with receive decode  utf 8

User · Answer

You can change the send line to this   c send b Thank you for connecting     The b makes it bytes instead

User · Answer

An alternative solution is to introduce a method to the file instance that would do the explicit conversion   import types  def  write str self  ascii str       self write ascii str encode  ascii     source file   open  myfile bin    wb   source file write str   types MethodType  write str  source file    And then you can use it as source file write str  Hello World

[python] Python sockets error TypeError: a bytes-like object is required, not 'str' with send function

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