1500 bytes is actually a pretty small buffer by today's standards.
Depending on the buffer contents, the length of the pattern, and the number
and length of "false starts" (prefixes of the pattern that appear in the
buffer), any one of several different algorithms might be the best/fastest.

The first-order solution is to use the strstr() library function, but that
will only work if your buffer doesn't contain embedded nulls.

If you really do need a high-end algorithm, do some searching for the
Boyer-Moore algorithm or the Knuth-Morris-Pratt algorithm.  Both are well
described in online resources and source code implementations are available
if you do some hunting.  For the size of your buffer, it's entirely possible
that a brute-force search will be as fast as these fancy algorithms, so you
should code up the brute-force solution (or use strstr) for comparison and
keep whichever gives the best performance on your particular data.

-cd