[协议名] contains 字符串（或16进制），eg：
比如查找sip协议包含某个事务的所有报文，这个事务id的末尾几位对应的十六进制为：
67:61:62:72，就可以用sip contains 67:61:62:72来找到。
对于http协议可以简单的用http contains baidu.com来过滤
ip.addr == 10.0.0.1 [Sets a filter for any packet with 10.0.0.1, as either the source or dest]
2. ip.addr==10.0.0.1 && ip.addr==10.0.0.2 [sets a conversation filter between the two defined IP addresses]
3. http or dns [sets a filter to display all http and dns]
4. tcp.port==4000 [sets a filter for any TCP packet with 4000 as a source or dest port]
5. tcp.flags.reset==1 [displays all TCP resets]
6. http.request [displays all HTTP GET requests]
7. tcp contains traffic [displays all TCP packets that contain the word ‘traffic’. Excellent when searching on a specific string or user ID]
8. !(arp or icmp or dns) [masks out arp, icmp, dns, or whatever other protocols may be background noise. Allowing you to focus on the traffic of interest]
9. udp contains 33:27:58 [sets a filter for the HEX values of 0x33 0x27 0x58 at any offset]
10. tcp.analysis.retransmission [displays all retransmissions in the trace. Helps when tracking down slow application performance and packet loss]
