tcp_close

Builtin index · Concurrency

tcp_close(sock)

Input: sock · Output: no output

What it is

sock must be a TcpConn handle (from tcp_accept/tcp_connect) — not a TcpListener; calling it on a listener errors, since a listener has no explicit close and simply releases its OS socket when the handle is dropped. Shuts the connection down and marks it closed; returns none. Idempotent — closing an already-closed connection is a harmless no-op, not an error.

Overloads

One call shape — this function is not overloaded.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

function echo_once(listener)
    conn = tcp_accept(listener)        # blocks for the one client

    msg = tcp_recv(conn)
    tcp_send(conn, msg)
    tcp_close(conn)
end function

listener = tcp_listen(0)               # 0 -- let the OS pick a free port

port = tcp_port(listener)
w = spawn("echo_once", listener)

client = tcp_connect("127.0.0.1", port)
tcp_send(client, "hello")
print(tcp_recv(client))                # "hello" -- echoed back

tcp_close(client)
join(w)

hello

from concurrency

How it works

tcp_close(conn) shuts down both directions and releases the socket; closing an already-closed connection is a no-op, matching close(f)'s own idempotence above.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.