TAPPING INTO SHORE-BASED WI-FI clients on the boat (wired or wireless) are normally assigned by a shore-based DHCP server. The problem is that the wireless Ethernet bridge will typically have a fixed IP address for management that won't necessarily be on the same subnet as IP addresses set by shore-based DHCP servers, preventing networked clients from directly managing the wireless Ethernet bridge.
Two possible solutions to this problem are 1) to use two network adapters (wired or wireless) on a given networked client, one configured by (shorebased) DHCP for Internet access, and the other configured manually just for managing the wireless Ethernet bridge. Or 2) use a multi-homed Ethernet adapter with both a static address and a DHCP address.
mize possible interference, a boat Wi-Fi access point should ideally be on a different minimally-overlapping channel (1, 6, 11 in the USA) from the shore access point. Power — Many stand-alone low-end networking devices that use separate brick-style power supplies are able to
Wired versus Wireless Clients — It's important to note that in order to mini-
ACCESSING SAILMAIL & WINLINK VIA WI-FI N
ow that you have a working Wi-Fi connection and can browse the web, how do you get your mail from SailMail or Winlink? Both systems offer access via Internet in addition to radio. The details differ a bit, we'll discuss them in turn and try to keep the confusion to a minimum. SailMail offers four ways to get your messages: radio, direct Internet access, a pop3 email server, and webmail using your web browser. Radio doesn't usually work very well in marinas because of the electrical interference from battery chargers and other AC-powered electrical equipment, so use one of the Internet alternatives wherever Wi-Fi is available. The simplest way is to use Airmail's Internet access window (called a 'Telnet' window on older Airmail versions). Just click the 'Internet' button on the toolbar (looks like a 'lightning bolt'), select one of the two SailMail 'stations' and click the green 'connect' button. It works just like radio (except much faster), and messages are sent and received in the same fashion. This method also works on Iridium sat phones and, since the same compression and protocols are used as for the radio links, it is very efficient — there is no need to use a separate compression service. One problem that has been popping up is marinas blocking the Internet ports that are used for special services such as SailMail's Internet connection. Both SailMail servers monitor both port 50 and 50001, so if one doesn't work then try the other (click the 'settings' button in the Internet window). If still no luck, then the next trick is to use Airmail's mail client window Page 160 •
• April, 2007
and access SailMail's POP3 server like a normal email program. This is written up in the Airmail help file under 'SailMail, POP server', and will usually work because very few marinas block the standard email ports (El Cid in Mazatlan being a notable exception — they block everything). And if all else fails, then fire up the web browser and go to www.sailmail.com and click on 'Webmail'. There are multiple choices described there, so be sure to read what is on the page. The problem with webmail is that the messages aren't easily transferred to the Airmail software, and aren't saved unless you specifically save them. One good way to keep an archive is to sign up for a (free) Google Gmail account, and use that as an archive. Whenever you get a message that you want to save, just forward it to your Gmail address. And if the web browser won't work then you really aren't connected to the Internet, back up and try Google.There is more information for SailMail members here: http://saildocs.com/internet. For Winlink the choices are radio (same issues in a marina), Internet (Telnet), or webmail. There are dozens of Internet/Telnet servers (listed in the 'MBO bulletin' under the View menu) and it can get confusing — see 'Winlink, Internet access' in Airmail's help file and find a fellow user to help you set it up. All of the stations use port 12001 which, again, may be blocked by some marinas. The other alternative is webmail — navigate your web browser to www.winlink. org and click on 'WebMail' on the left side. — jim corenman
tolerate a relatively wide range of input voltage, and can be run directly from 12 volt DC boat power with an appropriate adapter cable. Check manufacturer input voltage specs if possible. Relaying and Mesh Networks — When some boats are too distant from a shore access point for a direct Wi-Fi connection, it may be possible to setup nearer boats to repeat or relay the Wi-Fi signal to more distant boats. (See info on Navas' site.) International Use — Wi-Fi channels are standardized, but vary slightly in different parts of the world. Many Wi-Fi devices will work properly anywhere in the world, either by means of a configuration option (preferable), or by means of different firmware loads (clumsy). — john navas On his website, Navas lists a wealth of useful resource links. Among them are: • Wi-Fi Internet solutions for boaters and marinas — www.wifimarine.org • RadioLabs — www.radiolabs.com • MarineNet Wireless — www. marinenet.net/wifi • HyperLink Technologies — www. hyperlinktech.com • Linksys — www.linksys.com
The April 2007 issue of the West's premier sailing and marine magazine.