Sending hex-data via socket, is interpreted as string

Question

I'm new to python, and I'm trying to use a 3rd party library/module. What I'm doing now is:

s.send(rtp.header_bytes + rtp.payload) 
# -> \x80!\x00\x01\x00\x00\x00d\x00\x00\x00\x00Testy

to send the header and the payload of a packet via tcp socket. On the receiving side:

conn, addr = socket_rtp.accept()
data = conn.recv(1024)

the data is passed to a constructor __init__(self, bytes, length) and then used like this

self.version = (bytes[0] & Packet.V_MASK) >> 6

but it seems that it's interpreting the bytes array as string? I'm getting the following exception:

.... line 322, in __init__
    self.version = (bytes[0] & Packet.V_MASK) >> 6
TypeError: unsupported operand type(s) for &: 'str' and 'int'

Thank you for your help.

falsetru · Accepted Answer · 2014-07-18 14:48:36Z

1

To convert the string (bytes) to int, you can use ord (assuming your're using Python 2.x):

self.version = (bytes[0] & Packet.V_MASK) >> 6

self.version = (struct.unpack('B', bytes[0])[0] & Packet.V_MASK) >> 6

>>> ord('\x80')
128
>>> import struct
>>> struct.unpack('B', '\x80')[0]
128

answered Jul 18, 2014 at 14:48

falsetru

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2 Comments

This gives me: Struct() argument 1 must be string, not unicode. Also, I'm now confused why there is a '!' in the string representation...

@damian, Did you import __future__ (from __future__ import unicode_literal)? Then, use b'B' instead of 'B'.