[greybrunix]

I think the point is that a socket is doing both reading and writing using the same file descriptor, which is counterintuitive.

[Veserv]

Which is a problem of their own making. If they use two sockets, which would be needed if all three programs were on different machines, then it would work exactly the same as the pipe example.

The problem is that they saw TCP sockets are two-way and then thought to optimize the TCP connection/state overhead by using it for double-duty without applying appropriate abstractions to transparently use a two-way channel as two one-way channels.

[Gabrys1]

Some early protocols used two sockets for (maybe?) roughly this reason

[rnmmrnm]

and that to half-close a socket you need to use some unintuitive syscall.

[pif]

Use two pipes and you won't need to half-close any socket.