I think Xplico is a good choice, on bt4

"The goal of Xplico is extract from an internet traffic capture the applications data contained.
For example, from a pcap file Xplico extracts each email (POP, IMAP, and SMTP protocols), all HTTP contents, each VoIP call (SIP), FTP, TFTP, and so on. Xplico isnít a network protocol analyzer. Xplico is an open source Network Forensic Analysis Tool (NFAT).
Xplico is released under the GNU General Public License"