Conversion from Hexa to ascii how to detect packet

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C#

Windows

form

$$,,,,47,1,55200109400273000000B203029000110057616A6168003033343535313732383135000000000036313130312D303339303930352D3900542D3030303035370000000000*

$$,,,,47,1,55200109400257616A61686174204162626173000000003033343535313732383135000000000036313130312D303339303930352D3900542D3030303035370000000000*

$$,,,,47,1,F432400257616A61686174204162626173000000003033343535313732383135000000000036313130312D303339303930352D3900542D30303030353700000000000000*

From server i have receiving data in HEX form i want to detect a packet which is start from
($$,,,,47 and end at *)
Every time my server check if find packet that then start conversion
How can i detect these type of packet in my loop