The 20-year-old American downed Raonic 6-3, 5-7, 7-5 to set up a second-round meeting with James Blake.
Sock had played in only one previous match on the ATP circuit this year and brought a career pro record of 6-11 into the match. Sock is ranked 168th in the world and Raonic has climbed to No. 14.
Haas ousted Evgeny Donskoy 7-6 (8-6), 6-4 and Hewitt survived against Yen-Hsun Lu 2-7, 7-6 (7-3), 6-4.
In other first-round contests, Alexandr Dolgopolov defeated Bjorn Phau 6-3, 6-4 and Mannko Matsovek won over Go Soeda 7-6 (8-6), 6-4.
Top-seeded Marin Cilic will face Igor Sijsling in Thursday's second round.