Requirements : 1. Picophone Caller needs Picophone which is a freeware voip application.
2. A web server which offer FTP. You can use a free web host.
I personally use tripod.com for years without any problem.
I highly recommend to not use your official web site with Picophone Caller because does heavy use of FTP.

Functionality:
Picophone caller does two things in parallel.
a) Publish your IP in your web host via FTP
b) Scans from your user list the oher Picophone-callers users and let you know their ips.
Doing this you can see which friend is online and which is offline and if it is ONLINE you can call him by pressing the call button. If you want to go offline you just have to press the OFFLINE button .

Set Up :
1. Install PicoPhone
2. Get a free hosting plan (ex : tripod.com) and write down the ftp access data etc...
3. Log in to your web host with a ftp client and create an empty folder like picophone.
3. Unzip Picophone Caller
4. Configure Picophone caller (FTP host, user name, password, port, path, filename, auto-online, nickname and picophone port)
At path you must add a backslash. Example : picophone\
Please note that the default port of picophone is the 11676.
5. Set the picophone path (where is located picophone164.exe)
6. Now close the Picophone Caller, by doing this you save all the data
7. Re-open Picophone Caller

You are done ! Your Picophone caller data is located at :
www.yoursite.com/PATH/FILE_NAME.TXT for example :
myusername.tripod.com/picophone/PicoList.txt

All your picophone friends now have to do the same. You just have to add their feeds in your picophone caller list, this can be done by clicking on add site (user) button and add your friend's url.

Notes : Picophone has a free service called picoserver (look at the settings of picophone). This server let you to have nicknames but is not that stable and if goes down then noone can call to noone. Picophone Caller instead let to the users select the web provider so you are no more limited by picoserver. Of course you can use both services picoserver and Picophone Caller.

Tips :
1. Picophone caller can also be used only for IP publishing. If you have a remote server and you want his IP you can use Picophobe Caller for doing this job.

2. It is always good to have always running picophone and picophone caller when you start your computer so anyone can call you. Going at Start -> All programs -> Startup, rightclick it and press open. In this folder you can your shortcuts to picophone and picophone caller so evey time that your computer starts loads these two programs.