IPgrab is a verbose packet sniffer for UNIX hosts.

Example telnet output: 


----------------------------------------------------------------
                        Ethernet header (961445334.490653)
----------------------------------------------------------------
Hardware source:        00:10:4b:96:1d:a8
Hardware destination:   08:00:02:25:29:77
Protocol:               0x800 (IP)
Length:                 68
----------------------------------------------------------------
                        IP Header
----------------------------------------------------------------
Version:                4
Header length:          5
TOS:                    0x10
Total length:           54
Identification:         6795
Fragmentation offset:   0
Unused bit:             0
Don't fragment bit:     1
More fragments bit:     0
Time to live:           64
Protocol:               6 (TCP)
Header checksum:        37890
Source address:         149.112.60.156
Destination address:    149.112.36.168
----------------------------------------------------------------
                        TCP Header
----------------------------------------------------------------
Source port:            2692 (unknown)
Destination port:       23 (telnet)
Sequence number:        2876130028
Acknowledgement number: 3994633468
Header length:          8
Unused:                 0
Flags:                  PA
Window size:            32120
Checksum:               58743
Urgent:                 0
Option:                 1 (no op)
Option:                 1 (no op)
Option:                 8 (timestamp)
  Length:               10
  Timestamp value:      181028495
  Timestamp reply:      44432019
-----------------------------------------------------------------
0D 00                                            ..


And of a minimal mode TCP session: 


961445601.933843 00:10:4b:96:1d:a8->08:00:02:25:29:77 IP 149.112.60.156->198.186.203.44 (72,DF) TCP 2690->22 (PA,2794909852,2764779739,31856)  
961445602.086258 08:00:02:25:29:77->00:10:4b:96:1d:a8 IP 198.186.203.44->149.112.60.156 (52,DF) TCP 22->2690 (A,2764779739,2794909872,32120) 
961445602.086374 08:00:02:25:29:77->00:10:4b:96:1d:a8 IP 198.186.203.44->149.112.60.156 (96,DF) TCP 22->2690 (PA,2764779739,2794909872,32120)  
961445602.097106 00:10:4b:96:1d:a8->08:00:02:25:29:77 IP 149.112.60.156->198.186.203.44 (52,DF) TCP 2690->22 (A,2794909872,2764779783,31856)

The ipgrab homepage is located at:

	http://ipgrab.sourceforge.net