encoding instead of byte string concatenation, the client’s message is shown as byte
string explicitly here.
Other run modes: Local servers with Cygwin and remote clients
Also note that the server is running remotely on a Linux machine in the preceding
section. As we learned in Chapter 5, the fork call is not supported on Windows in
standard Python at the time this book was written. It does run on Cygwin Python,
though, which allows us to start this server locally on localhost, on the same machine
as its clients:
[Cygwin shell window]
[C:\...\PP4E\Internet\Socekts]$ python fork-server.py
Server connected by ('127.0.0.1', 58258) at Sat Apr 24 07:50:15 2010
Server connected by ('127.0.0.1', 58259) at Sat Apr 24 07:50:17 2010[Windows console, same machine]
C:\...\PP4E\Internet\Sockets> python echo-client.py localhost bright side of life
Client received: b"Echo=>b'bright' at Sat Apr 24 07:50:20 2010"
Client received: b"Echo=>b'side' at Sat Apr 24 07:50:20 2010"
Client received: b"Echo=>b'of' at Sat Apr 24 07:50:20 2010"
Client received: b"Echo=>b'life' at Sat Apr 24 07:50:20 2010"[Windows console, same machine]
C:\...\PP4E\Internet\Sockets> python echo-client.py
Client received: b"Echo=>b'Hello network world' at Sat Apr 24 07:50:22 2010"We can also run this test on the remote Linux server entirely, with two SSH or Telnet
windows. It works about the same as when clients are started locally, in a DOS console
window, but here “local” actually means a remote machine you’re using locally. Just
for fun, let’s also contact the remote server from a locally running client to show how
the server is also available to the Internet at large—when servers are coded with sockets
and forks this way, clients can connect from arbitrary machines, and can overlap arbi-
trarily in time:
[one SSH (or Telnet) window]
[...]$ python fork-server.py
Server connected by ('127.0.0.1', 55743) at Sat Apr 24 07:15:14 2010
Server connected by ('127.0.0.1', 55854) at Sat Apr 24 07:15:26 2010
Server connected by ('127.0.0.1', 55950) at Sat Apr 24 07:15:36 2010
Server connected by ('72.236.109.185', 58414) at Sat Apr 24 07:19:50 2010[another SSH window, same machine]
[...]$ python echo-client.py
Client received: b"Echo=>b'Hello network world' at Sat Apr 24 07:15:19 2010"
[...]$ python echo-client.py localhost niNiNI!
Client received: b"Echo=>b'niNiNI!' at Sat Apr 24 07:15:31 2010"
[...]$ python echo-client.py localhost Say no more!
Client received: b"Echo=>b'Say' at Sat Apr 24 07:15:41 2010"
Client received: b"Echo=>b'no' at Sat Apr 24 07:15:41 2010"
Client received: b"Echo=>b'more!' at Sat Apr 24 07:15:41 2010"[Windows console, local machine]806 | Chapter 12: Network Scripting