Python 3 socket int does not support the buffer interface

Question

I recently came across little troubles with python variables affectations. I affected the same variable with different types. For instance:

hello = 1
print(hello)
hello = "Hello"
print(hello)

The output is what I expect: it displays 1 and then hello.

But I have a problem with an echo server test script:

skt_o = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0)
skt_o.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
skt_o.bind(('', 7777))
skt_o.listen(1)
lst_skt = []

while(1):
    lst, _, _ = select.select(lst_skt+[skt_o], [], [])

    for s in lst:
        if(s == skt_o):
            skt, _ = s.accept()
            lst_skt.append(skt)
        else:
            res = s.recv(1500)

            if(len(dat) == 0):
                print("[R-Close] %s" % s)
                s.close()
                lst_skt.remove(s)
                break

            for c in lst_skt:
                if(c !=  s):
                    res = c.send(res)

I use nc localhost 7777 for connecting two terminals to the listening port. When I send a message everything work as expected. The two terminals can communicate. But when I launch a third terminal and try to send a message, I get a TypeError (int does not support the buffer interface).

if I replace the res variable as shown below everything work well. I can connect three and more terminals which can communicate:

dat = s.recv(1500)

if(len(dat) == 0):
    print("[R-Close] %s" % s)
    s.close()
    lst_skt.remove(s)
    break

    for c in lst_skt:
        if(c !=  s):
        res = c.send(dat)

What is the problem with the first echo script?

I know that the problem comes from this line:

res = c.send(res)

But I cannot explain why.

nb: I use Python 3.4.2

Thanks for your answers.

I doubt the errors are "random". What errors are you talking about? — Carcigenicate
– Carcigenicate, Commented Dec 21, 2016 at 4:11
I am trying to reproduce it don't remember the exact sentence but the compiler claimed that he could not affect the variable with a new type. — Papipone
– Papipone, Commented Dec 21, 2016 at 4:18
It was a TypeError when using sockets. I will post the code tonight, need to go to work. @Carcigenicate I doubt the errors are "random". Me too I may have made a mistake. Well, we will see tonight. — Papipone
– Papipone, Commented Dec 21, 2016 at 4:45
If it was a TypeError it's likely you were doing something like result = ''; result += sock.read(2048). Don't do that. BADTIE - bytes are decode, text is encoded. Or it may be something else, given that you don't know what the error actually is. — Wayne Werner
– Wayne Werner, Commented Dec 21, 2016 at 5:51

Papipone · Accepted Answer · 2018-11-05 02:42:25Z

This is because in python 3.4.x the send method of the socket object accepts a 'byte' sequence type as an argument. Thus you need to convert the argument you are passing to a byte by using a 'b' prefix with normal string syntax: b'python'. This converts the string python to a byte sequence type. So in your code you need to convert the res you are passing into the send method to a byte. Use something like this in your code instead. res = c.send(b'some-string-or-integer') check the python docs on built-in types, section 5.6 via the link below: https://docs.python.org/3.1/library/stdtypes.html

Also from the python docs too....

Also, while in previous Python versions, byte strings and Unicode strings could be exchanged for each other rather freely (barring encoding issues), strings and bytes are now completely separate concepts. There’s no implicit en-/decoding if you pass an object of the wrong type. A string always compares unequal to a bytes or bytearray object.

Collectives™ on Stack Overflow

Python 3 socket int does not support the buffer interface

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related