pwnat, pronounced "poe-nat", is a tool that allows any number of clients behind NAT gateways to communicate with a server behind a separate NAT with no port forwarding and no DMZ setup on any routers in order to directly communicate with each other. The server does not need to know anything about the clients trying to connect, nor does it need to communicate with any other hosts in order to initiate the communication. Simply put, this is a proxy server that works behind a NAT, even when the client is behind a NAT. There is no middle man, no proxy, no third party, no UPnP required, no spoofing, and no DNS tricks. More importantly, the client can then connect to any host or port on any remote host or to a fixed host and port decided by the server.
dnscrypt-proxy acts as a DNS proxy between a regular client, like a DNS cache or an operating system stub resolver, and a DNSCrypt-aware resolver, like OpenDNS. The DNSCrypt protocol focuses on securing communications between a client and its first-level resolver. While not providing end-to-end security, it protects the local network (which is often the weakest link in the chain) against man-in-the-middle attacks. It also provides some confidentiality to DNS queries.
Muse Proxy is a highly customizable multi-platform proxy server. It is easy to use and configure, acting successfully as a gateway to authenticated restricted content, rewriting Web server, Web Access Management, proxy server, and reverse proxy. It has been used for more than 10 years within the Muse Federated Search Platform to manage the authentication to resources and the navigation to full text, by restoring the server session on the end-user browser.
nassh-relay implements a relay server used with the Secure Shell (hterm) plugin for the Chromium Web browser. It tunnels ssh traffic through an HTTP xhr or websockets connection. It could be used as a gateway to route traffic to an internal network (it supports authentication on the HTTP endpoint) or simply as an ssh-over-HTTP proxy.