According to the US Army Register of Enlistments 1798-1914 (at Ancestry.com), Porter Shepard enlisted 24 March 1813 and 14 Feb 1814 at Hartford, CT. He was in the 25th MA Regiment. His service was 5 years. The record says he was born in West Springfield, Hampden, MA, is a farmer, 5' 2" tall, has gray eyes and light complexion.
In the 1840 census, Porter Shepherd is living in Hartford, Trumbull Co., OH. According to the census data, Porter is age 40-49, his wife is 30-39, and there is one girl under age 5.
I found his year of birth and death date online at a family tree. According to the tree, his parents were Simeon Thomson Shepard and Mary Lindley (or Lindsey), married 19 Nov 1795 at Westfield, Hampshire Co., MA.
(source: https://mostlyangels.com/g0/p173.htm)