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.

Answer 1

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:

1. 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).
2. For literals, add a 'b' for bytes string: c.sendall(b'Thank you for connecting')
3. 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.

Answer 2

You can decode it to str with receive.decode('utf_8').