捕获过滤器：
捕获http get ，post,put请求

0x47455420 ==>GET ascii码
GET 请求：port 80 and tcp[((tcp[12:1] & 0xf0) >>2):4] = 0x47455420
POST 请求：port 80 and tcp[((tcp[12:1] & 0xf0) >>2):4] = 0x504f5354
PUT 请求：port 80 and tcp[((tcp[12:1] & 0xf0) >>2):4] = 0x505554