Modem
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SonicOS 5.8.1 Administrator Guide
The next line has OK as the expected string, and the interpreters waits for OK to be returned
in response to the previous command, ATV1, before continuing the script. If OK is not returned
within the default time period of 50 seconds, the chat interpreter aborts the script and the
connection fails. If OK is received, the prefix and phone number of the selected dial-up account
is dialled. The \T command is replaced by chat script interpreter with the prefix and phone
number of the dial-up account.
In the last line of the script, CONNECT is the expected response from the remote modem. If
the modems successfully connect, CONNECT is returned from the TELE3 SP modem.The \D
adds a pause of one second to allow the server to start the PPP authentication. The \C
command ends the chat script end without sending a carriage return to the modem. The TELE3
SP then attempts to establish a PPP (Point-to-Point Protocol) connection over the serial link.
The PPP connection usually includes authentication of the user by using PAP (Password
Authentication Protocol) or CHAP (Challenge Handshake Authentication Protocol) from the
PPP suite. Once a PPP connection is established, it looks like any other network interface.
Custom Chat Scripts
Custom chat scripts can be used when the ISP dial-up server does not use PAP or CHAP as
an authentication protocol to control access. Instead, the ISP requires a user to log onto the
dial-up server by prompting for a user name and password before establishing the PPP
connection. For the most part, this type of server is part of the legacy systems rooted in the
dumb terminal login architecture. Because these types of servers can prompt for a user name
and password in a variety of ways or require subsequent commands to initiate the PPP
connection, a Chat Script field is provided for you to enter a custom script.
If a custom chat script is required by an ISP for establishing a connection, it is commonly found
on their web site or provided with their dial-up access information. Sometimes the scripts can
be found by using a search engine on the Internet and using the keywords, “chat script ppp
Linux <ISP name>”.
A custom chat script can look like the following script:
ABORT `NO CARRIER'
ABORT `NO DIALTONE'
ABORT `BUSY'
" ATQ0
" ATE0
" ATM1
" ATW2
" ATV1
OK ATDT\T
CONNECT "
sername: \L
assword: \P
Tip! The first character of username and password are ignored during PPP authentication.
The script looks a lot like the previous script with the exception of the commands at the end.
There is an empty string (") after CONNECT which sends a carriage return command to the
server. The chat interpreter then waits for sername: substring. When a response is returned,
the current PPP account user name, substituting the \L command control string, is sent. Then,
the chat interpreter waits for the substring assword:, and sends the password, substituting \P
with the PPP account password. If either the sername or assword substring are not received
within the timeout period, the chat interpreter aborts the dial-up process resulting in a dial-up
failure.
