What is the key combination to send NUL byte from a terminal?

This may sound ridiculous but I need to send something like <policy-file-request/> followed by a nul byte from a terminal to a XML socket server.

I am using PUTTY but I tried all sorts of combinations like \0 or /0 or \u0000 but to no avail.

I'm wondering if there is a s开发者_C百科pecific key combination for this or am I messing up somewhere?

It depends on what PuTTY is emulating (different emulators might map it differently) but it's typically ^@ -- that is, Ctrl + @.