Fletcher Dunn has been making video games professionally since 1996. He worked at Terminal Reality in Dallas, where as principal programmer he was one of the architects of the Infernal engine and lead programmer on BloodRayne. He was a technical director for The Walt Disney Company at Wideload Games in Chicago and the lead programmer for Disney Guilty Party, IGN's E3 2010 Family Game of the Year.
He has worked for Valve Software in Bellevue, Washington since 2011 and has contributed to Steam and all of Valve's recent games. He is the primary author of the GameNetworkingSockets networking library and the Steam Datagram Relay service
Oh, but his biggest claim to fame by *far* is as the namesake of Corporal Dunn from Call of Duty: Modern Warfare 2.