Added note to UNIX Tips page explaining how to connect a process' STDIO to a TCP...

diff --git a/data/notes/unix_misc.md b/data/notes/unix_misc.md
index 5b8b3a8..ea2a1bd 100644 (file)
--- a/data/notes/unix_misc.md
+++ b/data/notes/unix_misc.md
@@ -49,3 +49,42 @@ to a `(gdb)` prompt. Exit `gdb`.
 
 The characters have now been received by `vi` and a file should be waiting at
 `/tmp/vi_recover.txt`.
 
 The characters have now been received by `vi` and a file should be waiting at
 `/tmp/vi_recover.txt`.

+
+
+# Expose Process STDIO on TCP Port #
+
+This note explains how to launch a process and connect its
+`stdin`/`stdout`/`stderr` directly to a TCP port. It was tested on FreeBSD 12.
+
+As an example, we will launch a `bash` process running on a Debian 10 machine
+and connect it to TCP port `4242`. Then, from a FreeBSD machine we will connect
+and utilize the `bash` session remotely.
+
+First, on the Debian machine, we use
+[`socat`](http://www.dest-unreach.org/socat/), a program which establishes two
+bidirectional byte streams and transfers data between them. In our case, we
+tell `socat` to build a PTY at `/tmp/pty_test` and connect it to TCP port
+`4242`.
+
+    socat PTY,link=/tmp/pty_test,raw TCP-LISTEN:4242,reuseaddr,fork
+
+Note that the `PTY` argument to `socat` must precede the `TCP-LISTEN` argument.
+Despite the bidirectional nature, the endpoint definition order is not
+interchangeable.
+
+Now we use `setsid` to start a new `bash` process and attach it to the PTY at
+`/tmp/pty_test`. Note that we collapse `stdout` and `stderr` into a single
+combined stream.
+
+    setsid sh -c 'exec bash --login <> /tmp/pty_test >&0 2>&1'
+
+Replace `bash --login` with whatever other command you desire to execute. 
+
+Now, from the FreeBSD machine, connect the remote TCP port to your local STDIO
+with `socat`. Assuming the Debian machine running `bash` is at `192.168.1.107`,
+execute the following command.
+
+    socat STDIO,raw TCP:192.168.1.107:4242
+
+At this point you have a fully interative `bash` session running on the Debian
+machine, controlled from the FreeBSD machine.