File transfer on network

[MRAB]

mukesh tiwari wrote:
> Hello all
> Currently i am trying to develop a client and server in python. Client
> takes screenshot in every 20 seconds and send it to server. Server
> store the received file in folder. Here is code for Client
> 
> import sys
> import socket
> import gtk.gdk
> import time
> if __name__ == "__main__":
> 	s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);
> 	host,port="localhost",50007
> 	s.connect((host,port))
> 	while 1:
> 		w = gtk.gdk.get_default_root_window()
> 		sz = w.get_size()
> 		pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,sz[0],sz[1])
> 		pb = pb.get_from_drawable(w,w.get_colormap(),0,0,0,0,sz[0],sz[1])
> 		if (pb != None):
>                        pb.save('/home/tmp_1/screenshot.png',"png")
> 		f=open('/home//tmp_1/screenshot.png','rb')
> 		while 1:
> 			blk=f.read(2048)
> 			if not blk:break
> 			s.send(blk)
> 		f.close()
> 		print 'file transfer done';
> 		time.sleep(20)
> 
> 	s.close()
> 
> 
> Server Code
> import sys
> import socket
> import time
> if __name__ == "__main__":
> 
> 	s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
> 	host,port="",50007
> 	s.bind((host,port))
> 	s.listen(1)
>       conn,add=s.accept()
> 	i=0
> 	while 1:
> 		f=open('/home/tmp_2/copyscreenshot_'+str(i)+'.png','wb')
> 		while 1:
> 			data=conn.recv(2048)
> 			if not data:break
> 			f.write(data)
> 
> 		f.close()
> 		print 'file received'
> 		time.sleep(20)
> 		i+=1;
> 	#print ' file received '
> 
> 	conn.close()
> 
> 
> My problem is that server is copying only first image
> copyscreenshot_0.png while my client continuously taking screen shot.
> Kindly tell me what is wrong with my server code.
> 
The .recv will return an empty string only when the connection is closed
by the client, but the client keeps the connection open.

You could either open and close a connection for each image, or have the
client tell the server how many bytes it's going to send, followed by
the bytes (my preference would be to send the size as a string ending
with, say, a newline).

Another point: the .send method doesn't guarantee that it'll send all
the bytes (it'll return the number of bytes that it has actually sent);
use the .sendall method instead.