Replicating the behavior of a program?

I use an old program at work that connects to the internet and downloads some data. I used WireShark to see what the program did and the protocol seems very straight forward... The program uses TCP protocol and sends an ASCII command like FAF0f00001 and receives an ASCII response (FAF0f00131blablabla...) with the data I need, the 131 corresponds to the length of the string I'm receiving... How can I replicate the programs behavior based on the pcap file and using maybe C# to fool the server into thinking it's the program??