socat - socat is a relay for bidirectional data transfer between two independent data channels.
Modify Header Value (HTTP Headers) - Modify Header Value (HTTP Headers) is a browser extension that allows you to add, modify or remove a header for any request to your preferred domains.
Komodia Relay - Free open source tool to perform TCP based session relay
Sky Live HTTP Headers - Sky Live HTTP Headers is an open-source browser extension that visually displays HTTP requests and response headers from every website you visit.
PortMapper - Do you need to map a specific TCP or UDP port on your machine to another port on another machine?
ViewHTTPHeaders.com - View HTTP header response for any web page.