Show all packet contents traversing a port
tcpdump -s 0 -A 'tcp port 9200'
Show packets with a destination on a port
tcpdump -s 0 -A 'tcp dst port 9200
Voodoo to show the HTTP Header of packets destined for a port
tcpdump -s 0 -A 'tcp dst port 9200 and (tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x504f5354)'