franvergara66 franvergara66 - 1 month ago 8
Python Question

Send a file through sockets in Python

I'm trying to make a program in Python that implements sockets, each client sends a PDF file and the server receives it and the title is changed to "file_number.pdf" (i.e.: file_1.pdf). The problem presented is that only a client can send a file successfully. When a second client tries to send the program does crash. What am I doing wrong and how can I solve my code to allow N clients (with N <20) to connect to the server and transfer files?

Here's the server code:

import socket
import sys
s = socket.socket()
s.bind(("localhost",9999))
s.listen(10) # Acepta hasta 10 conexiones entrantes.
sc, address = s.accept()

print address
i=1
f = open('file_'+ str(i)+".pdf",'wb') # Open in binary
i=i+1
while (True):

# Recibimos y escribimos en el fichero
l = sc.recv(1024)
while (l):
f.write(l)
l = sc.recv(1024)
f.close()

sc.close()
s.close()


Here's the client code:

import socket
import sys

s = socket.socket()
s.connect(("localhost",9999))
f = open ("libroR.pdf", "rb")
l = f.read(1024)
while (l):
s.send(l)
l = f.read(1024)
s.close()


To simplify my code I always use a book with file name "libroR.pdf", but in the full code it is chosen by a graphical user interface.

Answer

You must put all the code from sc, address = s.accept() upto sc.close() into another loop or the server simply terminates after receiving the first file. It doesn't crash, the script is just finished.

[EDIT] Here is the revised code:

import socket
import sys
s = socket.socket()
s.bind(("localhost",9999))
s.listen(10) # Acepta hasta 10 conexiones entrantes.

while True:
    sc, address = s.accept()

    print address
    i=1
    f = open('file_'+ str(i)+".pdf",'wb') #open in binary
    i=i+1
    while (True):       
    # recibimos y escribimos en el fichero
        l = sc.recv(1024)
        while (l):
                f.write(l)
                l = sc.recv(1024)
    f.close()


    sc.close()

s.close()

Note that s.listen(10) means "set maximum accept rate to 10 connections", not "stop after 10 connections".