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Is there an application where I can run another application and it will allow me to see and more important manipulate the TCP data sent to another server?

I'm using Wireshark to view the data, but I want to alter it on the fly. Is there a way of doing that?

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You can use a tool called netsed to achieve this.

I have used this on linux . The syntax for replacement with regular expression is same as "sed" tool but i think all the functionality of sed is not there in netsed.

On Windows you might have to run it with Cygwin.

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Fiddler is the tool for that job, you just have to configure your application to use a proxy and you can then modify requests on the fly.

I assumed you were talking about HTTP but if you want to do the same thing with any TCP traffic have a look at those tools:

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Is this only for web content? the requests I want to manipulate are not web requests.. – user122926 Mar 14 '12 at 10:51
@user122926 - TCP packets are TCP packets....http traffic is tcp traffic. How about try it? – Ramhound Mar 14 '12 at 12:48

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