Manually using GPRS

Revision as of 16:10, 18 August 2007

You need to have GSM parts already initialized, with modem logged in to the network, for this to work. It is best to test it by doing test call. The GPRS connection is made using the PPP protocol to a server identified by an "APN" at the network operator.

Depending on the APN, you may need password authentication using CHAP or PAP. You can add the following default line for "password-less" connections:

# client        server  secret                  IP addresses
*               *       ""                      *

For CHAP, lines in /etc/ppp/chap-secrets are used. For PAP, the lines are in /etc/ppp/pap-secrets. The client should match the "user" option in pppd the config file (below). You can use * to mean any here, but the option user "" doesn't mean empty!

For example:

# Secrets for authentication using CHAP
# client        server  secret                  IP addresses
*               *       ""                      *
"gprs"          *       "gprs"                  *
"eplus"         *       "gprs"                  *  

You'll need /etc/ppp/peers/gprs:

# File:
# gprs
#
# Description:
# This file holds the pppd options for GPRS

# To give some debug info (could be provided on command line too)
# debug

# To keep pppd output on the terminal (could be provided on command line too)
nodetach

# Serial device to which the GPRS modem is connected
/dev/ttySAC0

# Serial port line speed
115200

# use hardware flow control
crtscts
#nocrtscts

# time between retries
holdoff 3

# Connect script
connect /etc/ppp/peers/gprs-connect-chat

# Disconnect script
disconnect /etc/ppp/peers/gprs-disconnect-chat

# IP addresses:
# - accept peers idea of our local address and set address peer as 10.0.0.1
# (any address would do, since IPCP gives 0.0.0.0 to it)
# - if you use the 10. network at home or something and pppd rejects it,
# change the address to something else
:10.0.0.1

# pppd must not propose any IP address to the peer!
noipdefault

# Accept peers idea of our local address
ipcp-accept-local

# No ppp compression
novj
novjccomp

# Add default route
defaultroute

# Replace any other default route for the time of the connection:
replacedefaultroute

# very long timeouts (unwise?)
lcp-echo-interval 300
lcp-echo-failure 40000

# don't require the other end to authenticate to us
noauth

# username to use for authentication, should match "client" in /etc/ppp/{chap,pap}-secrets
user "gprs"    ## opt out for eplus/pap
#user "eplus"  ## opt in for eplus/pap

And you'll need /etc/ppp/peers/gprs-connect-chat (needs "chmod +x"):

#!/bin/sh
#
# File:
# chat-gprs-connect
#
# Description:
# chat script to open Sonera GPRS service with GPRS phones. If ppp
# negotiation stalls, try restarting the phone. To try with other GPRS
# operator setting, change the PDP contex setting. The settings work with
# all Ericsson models, but Nokia 8310 does not suppor QoS parameters with
# AT commands, so just delete those lines and it'll work.
#
# Set PDP context CID=1, protocol=IP, APN=internet:
# AT+CGDCONT=1,"IP","internet","",0,0
#
# Set CID=1 QoS requirements from the network, not supported by 8310:
# AT+CGQREQ=1,0,0,0,0,0
#
# Set CID=1 minimum acceptable QoS parameters, not supported by 8310:
# AT+CGQMIN=1,0,0,0,0,0
#
# 'Call' CID=1 (activate PDP context one, perform GPRS attach):
# ATD*99***1#
#
# The actual chat script:
exec chat                                               \
TIMEOUT         22                              \
ECHO            ON                              \
ABORT           '\nBUSY\r'                      \
ABORT           '\nERROR\r'                     \
ABORT           '\nNO ANSWER\r'                 \
ABORT           '\nNO CARRIER\r'                \
ABORT           '\nNO DIALTONE\r'               \
ABORT           '\nRINGING\r\n\r\nRINGING\r'    \
SAY             "Press CTRL-C to close the connection at any stage!"    \
SAY             "\ndefining PDP context...\n"   \
""              "\d" \
""              "atz" \
OK              "ate1" \
OK              'at+cgdcont=1,"ip","internet","0.0.0.0",0,0' \
TIMEOUT         22      \
OK              ATDT*99***1#    \
TIMEOUT         22              \
SAY             "\nwaiting for connect...\n"    \
CONNECT         ""                              \
SAY             "\nConnected." \
SAY             "\nIf the following ppp negotiations fail,\n"   \
SAY             "try restarting the phone.\n"

You will need to adjust the APN name "internet" in at+cgdcont line to match what your network operator provides.

Also good to have is /etc/ppp/peers/gprs-disconnect-chat (needs "chmod +x"):

#!/bin/sh

exec /usr/sbin/chat -V -s -S    \
ABORT           "BUSY"          \
ABORT           "ERROR"         \
ABORT           "NO DIALTONE"   \
SAY             "\nSending break to the modem\n"        \
""              "\K"            \
""              "\K"            \
""              "\K"            \
""              "+++ATH"        \
""              "+++ATH"        \
""              "+++ATH"        \
"NO CARRIER"    ""              \
SAY             "\nPDP context detached\n"

Then, after initializing GSM, you should be able to initialize GPRS by pppd call gprs. Good luck!

To dial in - and get verbose output - use pppd

pppd debug call gprs

Some APN names for reference: