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<H2><A NAME="SECTION009220000000000000000">
7.2.2 Example</A>
</H2>

<P>
Here are two minimal example programs using the TCP/IP protocol: a
server that echoes all data that it receives back (servicing only one
client), and a client using it.  Note that a server must perform the
sequence <tt class=function>socket()</tt>, <tt class=method>bind()</tt>, <tt class=method>listen()</tt>,
<tt class=method>accept()</tt> (possibly repeating the <tt class=method>accept()</tt> to service
more than one client), while a client only needs the sequence
<tt class=function>socket()</tt>, <tt class=method>connect()</tt>.  Also note that the server
does not <tt class=method>send()</tt>/<tt class=method>recv()</tt> on the 
socket it is listening on but on the new socket returned by
<tt class=method>accept()</tt>.

<P>
<dl><dd><pre class=verbatim>
# Echo server program
from socket import *
HOST = ''                 # Symbolic name meaning the local host
PORT = 50007              # Arbitrary non-privileged server
s = socket(AF_INET, SOCK_STREAM)
s.bind(HOST, PORT)
s.listen(1)
conn, addr = s.accept()
print 'Connected by', addr
while 1:
    data = conn.recv(1024)
    if not data: break
    conn.send(data)
conn.close()
</pre></dl>

<P>
<dl><dd><pre class=verbatim>
# Echo client program
from socket import *
HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
s = socket(AF_INET, SOCK_STREAM)
s.connect(HOST, PORT)
s.send('Hello, world')
data = s.recv(1024)
s.close()
print 'Received', `data`
</pre></dl>

<P>
<div class=seealso>
  <p class=heading><b>See Also:</b></p>

<div class=seemodule>
<p>Module <b><tt class=module><a href="module-SocketServer.html">SocketServer</a></tt></b>&nbsp;&nbsp;&nbsp;(classes that simplify writing network servers)</p>
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