multiple send from server to client python

Question

First I am sending the requested file from the server to the client and after that I want to send the computed sha of the file from the server to the client, so that the client can check if both the sha from the sent and the received files are the same.

I manage to send the file but when I try to also send the sha (which is a variable) I receive a error ( i believe that the sha is also added to the file content)

How can i send them separately?

if (reqCommand == 'get'):
    with open (reqFile, 'rb') as in_file, open(encFile, "wb") as out_file:
        encrypt(in_file, out_file, "abc")
        f = open(encFile,'rb')
        for data in f:
            # print 'here3'
            conn.sendall(data)
        f.close()

        file_sh = hashfile(reqFile)
        print 'the sha1 function from the server: ', file_sh
        conn.send(file_sh)

and the client:

while True:
    data = sock.recv(1024)

    if not data:
        break
    #print data
    file_to_write.write(data)

CristiFati · Accepted Answer · 2020-06-19 18:30:39Z

1

You should redesign a bit how your app works:

First the servers sends to the client the file size
The client reads the file size (converts it to a number) and notifies the server (sends "OK" to the server for example)
The server reads the "OK" from the client and starts to send the file contents (preferably in smaller chunks)
The client keeps reading data until either it reads exactly "file size" bytes or error occurs
If no error occurred the client computes the hash of the file that it just received and sends it to the server
The server reads the hash from client and compares with the one of its local file - if they match it sends "OK" to the client "ERROR" otherwise
The client reads the response from server: if "ERROR" is received the file is deleted

edited Jun 19, 2020 at 18:30

answered Jun 3, 2015 at 9:13

CristiFati

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4 Comments

spoke Over a year ago

could you give me a short example please? i am still facing issues

CristiFati Over a year ago

where exactly are you having problems?i am not sure how to write code in comments.

CristiFati Over a year ago

Got to run, i'll probably take a look later or tomorrow.

spoke Over a year ago

i've eventually solved the problem. thank you for detailing the steps

Yurippenet · Accepted Answer · 2015-06-03 09:17:40Z

0

A TCP stream needs to be formatted in both ends, since it is a stream not packets. I suppose you could look for a nullbyte ('\x00') which should signal end of file.

answered Jun 3, 2015 at 9:17

Yurippenet

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2 Comments

CristiFati Over a year ago

Binary files often have \0s in their content.

Yurippenet Over a year ago

I like @CristiFati's soltution. Send the length of the file, read that number of bytes then you know you're done.

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