At Sea: Paradigm (satellite phone) You get a certain amount free per week and can pay for more minutes, mobile when you are in range of land, Email and good old pen, paper or postcard. Facebook and social networking sites are blocked from service computer systems.
Desert: Internet cabins where you can use anything you like, again depending on the current situation, for numerous very good reasons all comms are taken down occasionally. Paradigm, email and pen and paper. No mobiles.
Other than that, man up and get on with the task at hand, as you age you'll learn to hate everyone at home and long for the distance anyway.
Since my day one thing that has improved dramatically for HM Forces when serving away is the massive technological advances in communications with your loved ones.
I remember many years ago receiving a letter from a pissed off Mrs F that she had not receive any mailes for some considerable time, the day after she posted the letter about 10 from me landed on her mat in Eastney MQ's. There was a grovelling apology from her amongst the next Shack drop.
In Afghan you could get Facebook. Your own laptop needed to have certain settings applied to it at forward locations but at least 20 minutes a day was sufficient to send emails etc.
If you find time during the day write a proper letter to your loved-ones, invest time in sharing your emotions etc and then when you get on-line just copy and paste the text in to an email and send it.
It is easy to stay in touch; it is particularly special if you make the effort to properly connect with those at home.