The country code for Sri Lanka is (00) 94.
When dialing Indian phone numbers simply remove the domestic intercity prefix (0) of that city and replace it by India's country code 0091, or in some communication centers by +91.
International Direct Dialling (IDD) facilities are available at city hotels, resorts, post offices and telecommunication centres.
Free Wi-Fi is offered in most hotels and A/C-guesthouses. For access codes ask at the reception.
The use of GSM cellphones is widespread inside Sri Lanka and the coverage is good. Most mobile network operators have sales offices at the airport, immediately behind the exchange counters. The two market leaders are Dialog Mobile and Mobitel. Apart from Dialog, Etisalat and Airtel provide cheap roaming rates to India in particular. All mobile operators offer cheap IDD Call rates.
If you want to use the internet, the best way is to buy a HSPA dongle and a Mobile Broadband connection. Dialog, Mobitel and Airtel offer prepaid Mobile Broadband services which can be activated and used immediately.