Secure Your Connection

Cellular data connections are not as susceptible to sniffing as Wi-Fi or even wired Ethernet connections. Although you can be reasonably sure that the person sitting next to you in a cafe isn't sniffing your network communications, we can't say the same for someone on the network between your cellular carrier and the Web server you're trying to get to. So, unless you trust everyone on the networks in between, you should follow the same common sense guidelines that you would on any public network:

• Use a VPN if you need to connect to any sensitive resources at your workplace.
• Use secure versions of Web pages when signing into Web-based email, e-commerce sites, or anything sensitive.
• If you have to log into a machine remotely, use secure tools such as SSH (http://www.ssh.com), OpenSSH (http://www.openssh.org), or PuTTY (http://www.chiark.greenend.org.uk/~sgtatham/putty/) instead of telnet and FTP.

Mac OS X and Linux Connections

As yet, the GC82 card is only officially supported on Windows, and will not work out of the box on Mac OS X or Linux. However, if you insert it into your PCMCIA slot on a Mac or Linux notebook, you'll find that the card is indeed detected. You'll also be able to create a PPP connection by dialing the pseudo-phone number *99#. However, once you connect, you'll get error messages. To fix this problem, you'll either need to use third-party drivers (Smith Micro has one in development), or hack around in the bowels of your notebook computer's operating system.

For those comfortable with patching, compiling, debugging, and installing source code, we provide the following directions without warranty or support of any kind. Proceed with caution, as the following patches may render your system to be less reliable or inoperable.

With that disclaimer out of the way, here's what you'll need to do to download PPP source code, make the necessary tweaks, recompile, and then install.

For Linux and Unix systems, the PPP source is at http://www.samba.org/ppp/. If you're on Mac OS X, go to the Darwin source code pages at http://www.opensource.apple.com/darwinsource/ and locate the correct version of Darwin that corresponds to your version of Mac OS X. You'll find the source code for PPP on that page.

Once you've obtained the source code for PPP, find the file named auth.c, and edit the Helpers/pppd/auth.c file. Find the function named bad_ip_adrs() and add the following code immediately after the line "addr = ntohl(addr);":

 /* Hack for Sony Ericsson GC82 to let 127.0.0.2 through */
 if (2130706434 == addr) {
  fprintf(stderr, "SE GC82 Hack: permitting 127.0.0.2\n");
  return 0;
 }

(2130706434 is the decimal representation of the four-byte 127.0.0.2.) Next, recompile and install PPP. You'll need to go through these steps each time an update to your Linux or Mac OS X installation replaces the version of PPP that you just hacked.

Checking Signal Strength on Mac OS X and Linux

If you're on a non-Windows platform, you won't have the benefit of the GC82 Manager, which reports your signal strength. However, you can still check the signal strength using a console serial program such as Minicom (http://alioth.debian.org/projects/minicom/) or kermit (http://www.columbia.edu/kermit/ck80.html). To connect to the GC82, you must specify the serial port. On a Mac, it is /dev/tty/tty.pccard-serial0. You can connect using kermit by running the command "kermit -l /dev/tty.pccard-serial0" as root and running the commands "set carrier-watch off" and "connect":

 # kermit -l /dev/tty.pccard-serial0 
 C-Kermit 8.0.209, 17 Mar 2003, for Mac OS X 1.0
  Copyright (C) 1985, 2003,
  Trustees of Columbia University in the City of New York.
 Type ? or HELP for help.
 (/Users/bjepson/) C-Kermit>set carrier-watch off
 (/Users/bjepson/) C-Kermit>connect
 Connecting to /dev/tty.pccard-serial0, speed 9600
  Escape character: Ctrl-\ (ASCII 28, FS): enabled
 Type the escape character followed by C to get back,
 or followed by ? to see other options.

Once you connect, you can use AT commands that should be familiar to you if you ever had to interact directly with a Hayes modem. The first command you must issue is AT+CFUN=1, which turns the cellular radio on. The AT+CSQ command reports the signal strength on a scale of 0-31:

 AT+CFUN=1
 OK
 AT+CSQ
 +CSQ: 11,99

Intrepid AT&T Wireless customers have been posting their own experiences with this card. See this thread for a round-up of postings describing how to get this card working under Mac OS X. Linux users should pay special attention to the first posting in that round-up, which includes explicit instructions for seting up pppd to work with this card.