How to send images via socket in Python?

Question

So is the server:

import socket
from PIL import Image
port = 8000
host = '127.0.0.1'
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.bind((host, port))
s.listen(5)



while True:
    conn, addr = s.accept()
    print('Conectado a {}'.format(addr))
    with open('logo_python.png', 'rb') as f:
        conn.send(f.read())
        l = f.read()
    #im = Image.open(l)
    #im.show()
        f.close()

print('Arquivo enviado')

And the customer:

import socket
from PIL import Image
host = '127.0.0.1'
port = 8000
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host, port))

print("Recebendo Dados...\n")
with open('recebido.png', 'wb') as f:
        print('file opened')
        print('Recebendo dados...')
        data = s.recv(4000)
        f.write(data)
        print(data)
        print("ENVIADO")
        f.close()
with open('recebido.png', 'rb') as f:
        im = Image.open(f)
        im.show()

print('Transferência completa!!!')
s.close()
print('Conexão encerrada.')

The error that appears:

    File "C:/Users/Diego Cândido/PycharmProjects/servarq/ClienteTeste.py", line 18, in <module>
    im = Image.open(f)
  File "C:\Users\Diego Cândido\AppData\Local\Programs\Python\Python37\lib\site-packages\PIL\Image.py", line 2618, in open
    prefix = fp.read(16)
  File "C:\Users\Diego Cândido\AppData\Local\Programs\Python\Python37\lib\encodings\cp1252.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x9d in position 172: character maps to <undefined>

Basically what the server is sending to the client is:

b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x02Y\x00\x00\x00\xcb\x08\x06\x00\x00\x00]\xc9\x86&\x00\x00\x00\x04sBIT\x08\x08\x08\x08 #... e assim por diante

Answer 1

EDIT: Now with the code and the error is much easier to help.

UnicodeDecodeError occurs when trying to turn into a string a byte sequence that does not match the encoding used.

From the error text, it seems that it is using the encoding charmap cp1252; this would only occur if you were trying to run the method .decode() or if you opened the file in text mode (not binary); when you open a file in text mode, python does the automatic decoding.

The code you put in the question has the letter 'b' in the open, indicating binary mode:

with open('recebido.png', 'rb') as f:

To check if there was any mistake, I did a test with a JPG file I downloaded here, called diego.jpg. I opened it in text mode, without the letter b:

>>> f = open('diego.jpg', 'r', encoding='cp1252') # sem o 'b'
>>> f.read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/encodings/cp1252.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x90 in position 383: character maps to <undefined>

As you can see the error was quite similar to yours - I believe that when testing, you must have confused the files and left the open() without the b, And that’s why you got the mistake you made, I can’t see any other reason.

I then resolved test your code above, but with that file diego.jpg I downloaded. I only changed the name of the logo_python.png for diego.jpg and ran the server.

I changed the name of the recebido.png for recebido.jpg and surrounded the customer. Gave the following error:

Traceback (most recent call last):
  File "cliente.py", line 19, in <module>
    im.show()
#  ( ... )
  File "/usr/lib/python3/dist-packages/PIL/Image.py", line 1982, in show
    _show(self, title=title, command=command)
  File "/usr/lib/python3/dist-packages/PIL/ImageFile.py", line 228, in load
    "(%d bytes not processed)" % len(b))
OSError: image file is truncated (3 bytes not processed)

As you can see, 4000 bytes is not enough to transfer the image. I once again edited the client, and increased the number to 6502 (which is exactly the image size diego.jpg):

In short: It worked, your code is "working", the error you are having is impossible to occur with the code the way you put in the question, there must be some mistake. The only thing I changed was the number of bytes, which should be exactly the size of the image, because with fewer bytes it is not possible to open the image.