WPE Pro for Linux ?

I need some alternative to WPE Pro that will run in Linux. Here is the description of WPE Pro:

WPE Pro is a professional (commercial) version of Winsock Packet Editor. It is used to analyze network traffic and extract sensitive information like passwords or any other data sent through network.

But it is not just any packet-sniffer. You choose a process and then anything that process sends and revcieves will be logged in seperate packages. You can the re-send a packagde og even modify the package and send it. It work on anything, not just HTTP - it works with Java, Flash etc. anything that sends packages.

But is there anything like it for Linux?

If I remember correctly WPE is a TCP/IP Packet sniffer. It captures local packets being sent and received from your current box. I have no clue of any for Linux but im sure google can bring some up. If all fails just write one in C++ / C or something. Should be fun and fairly easy :P Plus it will do exactly what you want, not what the other developer wanted.