Q: Change ProtocolType of a Socket?

[Casper]

I am opening a socket and doing a TraceRoute to a server online, the
result of this is that I successfully identify the NAT server I am
going through as gateway.

In the next step I would like to know which port I have been mapped to
on this NAT. I plan to scan from the inside (local source routing)
sending packages to "the potential ports" on the public IP I just
uptained. The result thus being that (eventually) I will know which
public IP and port I have been assigned to by the NAT.

The question is then. Can I "convert" my socket to use another
protocol than the ICMP I have used for the pinging? I can not create a
new socket as this would assign to a new IP/port leaving me back where
I started. Unfortunately in C# setting .ProtocolType is a read-only
property. :(

Am I trying the impossible here? It would ofcourse be best if I can
accept TCP connections on my socket but if UDP is the only solution
then that's ok.

---
s = new Socket(AddressFamily.InterNetwork, SocketType.Raw,
ProtocolType.Icmp);

// Illigal
s.ProtocolType = ProtocolType.Tcp;
---


Suggestions would be greatly appreciated,
Thanks in advance,
Casper Bang, Denmark.

PS: The technique I am trying to implement is known as "UDP hole
punching" in RFC