Hardware Reference
In-Depth Information
Next, you need to tell the program to try connecting to the IRC server speciied in the vari-
ables at the start of the program. Type the following lines:
print 'Connecting to %(host)s:%(port)s...' % irc
try:
s.connect((irc['host'], irc['port']))
except socket.error:
print 'Error connecting to IRC server Æ
%(host)s:%(port)s' % irc
sys.exit(1)
he
try
and
except
commands are included in this code for
error handling
. If the system
fails to connect to the server—because the Pi isn't connected to the Internet, for example, or
because the server is down for maintenance—the program will print an error message and
gracefully exit. he
s.connect
line tells the socket module to try connecting to the IRC
server, using the
host
and
port
variables held in the
irc
dict.
If the program doesn't quit from the exception, it has successfully connected to the IRC
server. Before you can get a list of names in a channel, however, you need to identify yourself
to the server and issue some commands using the
send
function of the
socket
module.
Type the following lines into the program:
s.send('NICK %(nick)s\r\n' % user)
s.send('USER %(username)s %(hostname)s Æ
%(servername)s :%(realname)s\r\n' % user)
s.send('JOIN %(channel)s\r\n' % irc)
s.send('NAMES %(channel)s\r\n' % irc)
he
send
function works in almost exactly the same way as the
print
function, except that
instead of printing to the standard output—usually the terminal window or console—it
sends the output through the network connection. In this case, the program is sending
strings of text to the IRC server and telling it to register the program using the nickname
held in the
nick
variable and the user details held in the
username
,
hostname
,
server-
name
and
realname
variables. Next, the program sends the command to join the channel
speciied in the
channel
variable, and inally, it sends the command to receive the list of
users in that channel. Although this example is tailored to IRC, the same basic principle can
be used to issue commands to any network service—with modiications, this program could
be used to list the iles on an FTP server, or unread emails on a POP3 server.
