Open the single TCP terminal line to the PDP-10.

Idempotent: if the line is already open this reports status instead of reconnecting. The connection is owned by the server and survives any gap between tool calls. Nothing reconnects automatically -- if the session dies you will be told, and reopening is your explicit decision.

ITS ignores all input on a fresh line until it receives a literal ^Z, so the usual next step is send("~z").

Send input to ITS and return the output it produced.

A CR (0x0D) is appended automatically -- that is what the line editor wants -- unless input ends with the ~- marker or raw is true. Any literal LF/CRLF in input is normalised to CR, because a bare LF is a DDT command (examine next location) rather than a newline.

Returns only output produced since the previous call, plus a one-word end reason: matched, quiet, timeout, more_limit or dead.

Examples: send("z") calls ITS; send("fooej") sends f-o-o ESC j CR, the DDT altmode form usually written foo$j; send(":login rms", expect="@").

Collect further output without sending anything.

For slow programs, or to continue after a more_limit. Same cursor semantics as send: only output not already returned.

Re-show recent scrollback without consuming it.

Does not move the read cursor, so send and read still return the same output afterwards. Use this to recover lost context.

Connection state, target, uptime, pending output and any death reason.

Hard-close the line so the emulator frees it for the next connection.