Reading and writing TCP header (options) in Java

Question

What I'm trying to do is: Writing client and server for sending a String via TCP with Java, so far no problem using Socket and Input-/Output-Streams.

But now I'm trying to add 3 numbers to the "Options" field in the tcp header . I can't find any helpful tutorials or something else on how to customize the header and how to read it.

Any suggestions?

Answer 1

You can't:

• at application level, you do not have access to the TCP headers;
• Java does not have raw sockets either.

You can somewhat influence some of the TCP behavior by setting different socket options, though. But not manipulating TCP headers directly.

Answer 2

Not without utilizing external library like jNetPcap. jNetPcap does allow you to format and send your own packet.

jNetPcap Installation Guide (Eclipse)

jNetPcap Installation Guide (NetBeans)

A very rough sample code for formatting and sending packet. Rough it may be, but it shows you the possibilities to customize the packet.

Edit: Forgot to mention that jNetPcap is a Java wrapper for libpcap. They are meant to be utilized to read the packet in the first place.