Client Not Receiving Data in Python

Question

I am very new to Python and have a basic question, can a client side of a network socket connection make receive data? In my question, the client is the one who initiates the connection, which is probably obvious but I wanted to be clear. I ask because I have another server and client (both python) that allows the server to receive a file from the client. It works perfectly but I cannot get an example where the client receives a file. Python keeps telling me that the pipe has been broken and I suspect its because on the client side I use the line data = mysocket.recv(1024). My suspicion is that client doesn't see any data flowing and thus closes the connection to the server. The server sees it as a broken pipe. The server and client are below.

server:

 #libraries to import
 import socket
 import os
 import sys
 import M2Crypto as m2c

 #information about the server the size of the message being transferred
 server_address = '10.1.1.2'
 key_port = 8888
 max_transfer_block = 1024

 FILE = open("sPub.pem","r")

 #socket for public key transfer
 keysocket = socket.socket( socket.AF_INET, socket.SOCK_STREAM)
 keysocket.bind((server_address, key_port))
 keysocket.listen(1)

 while 1:
         conn, client_addr = keysocket.accept()
         print 'connected by', client_addr
         #sends data to the client
         data = FILE.read()
         keysocket.sendall(data)
 keysocket.close()

Client:

 # the specified libraries
 import socket
 import M2Crypto as m2c
 #file to be transferred
 FILE = open("test.txt", "r")
 #address of the server
 server_addr = '10.1.1.2'
 #port the server is listening on
 dest_port = 8888

 data = FILE.read()


 #Creates a socket for the transfer
 mysocket = socket.socket( socket.AF_INET, socket.SOCK_STREAM)
 mysocket.connect( (server_addr, dest_port) )

 data = mysocket.recv(1024)
 print data
 #creates a new file to store the msg
 name = "serverPubKey.pem"

 #opens the new file and writes the msg to it
 FILE = open (name, "w")
 FILE.write(data)


 #closes the socket.
 mysocket.close()

I would appreciate any help on the matter. Thanks!

Answer 1

Also, adding onto the previous comment, a good test sometimes is to repeat the receive a few times. The chance of the one pass catching the information the server sends is unlikely.

something like this

nreceive = True#nreceive = Not Received
ticks = 0
f = None
while nreceive and ticks < 101:#try to get the info 100 times or until it's received
    ticks+=1
    try:
        f = mysocket.makefile('rb')
        if not f == None:
            nreceive = False
    except:
        pass
data = f.read(1024)

Answer 2

In applications like this, it is sometimes helpful to bypass the low level detail and use socket.makefile with its higher-level API instead.

In the client close, replace:

data = mysocket.recv(1024)

with:

f = mysocket.makefile('rb')
data = f.read(1024)           # or any other file method call you need

The source code for ftplib shows how to do this in production code.