The nice thing is that we have applications that give us this. E.g. this is literally how ssh(1) works when used as a transport layer. (You have stdin, stdout,

The nice thing is that we have applications that give us this. E.g. this is literally how ssh(1) works when used as a transport layer. (You have stdin, stdout, and also stderr). The only issue is some in-band signaling on stderr and error codes when SSH itself has problems.