piping-server VS yamux

You can self-host easily on Heroku, Replit, Glich, etc. See https://github.com/nwtgck/piping-server/wiki/How-to-self-host-Piping-Server for detail.

I found a higher transparent way that uses existing and widely used commands: nc and curl. The original idea of a port forwarding with socat, curl, and Piping Server was proposed in a Japanese article by @Cryolite. Meanwhile, this post introduces a way using nc (netcat), which is more widely used and installed than socat, and the way allows simple integration with other commands using Unix pipe. It is very helpful when using an untrustable server because we can integrate it with an encryption command such as openssl.

tunnel - This one is a Golang library, not a program you can just run. However, it looks easy to use for creating custom solutions. Uses a single TCP socket, and yamux for multiplexing.

A simple solution is to multiplex TCP requests over Unix pipe. In order to multiplex TCP requests, Yamux is available created by Hashicorp, who creates Vagrant, Terraform, and so on. The protocol of Yamux is inspired by SPDY, which is the basis of HTTP/2 specification. The protocol spec is found in https://github.com/hashicorp/yamux/blob/master/spec.md. libp2p, which is used in IPFS, also uses Yamux as one choice of multiplexes and maintains Go and Rust versions of Yamux libraries.

If so, the answer is probably to put down the protobuf library entirely and just use yamux. Then you just get various net.Conns you can work with and you ignore the entire multiplexing problem.