# Read the greeting a server sends UNPROMPTED on connect, with a real timeout.
#
# Deliberately not xinetd-client.tcl: that one is shaped around request/response
# (send a payload, read the answer), and every service it drives stays silent
# until spoken to. SSH is the other shape -- RFC 4253 has the server send its
# version string first, before the client says anything -- so the useful probe
# here sends nothing at all and just reads. Keeping it separate also means the
# openssh suite does not break if the xinetd suite is ever retired.
#
# busybox nc on this image is the minimal applet (no -w), so a server that holds
# the connection open would hang the suite with no way to bound it; tcl's
# socket + a bounded [after] is what makes this safe to run against a daemon
# that may be half-working.
#
# argv: <port> [timeout-ms]
# prints exactly one line:
#   RESULT connfail <reason>   -- connect() failed (nothing is listening)
#   RESULT ok banner=<line>    -- connected; first line, CR/LF stripped
#   RESULT ok banner=          -- connected but the server said nothing in time
proc onread {s} {
    if {[eof $s]} { set ::done 1; return }
    append ::buf [read $s]
    if {[string first "\n" $::buf] >= 0} { set ::done 1 }
}

set port [lindex $argv 0]
set ms   [lindex $argv 1]
if {$ms eq ""} { set ms 5000 }

if {[catch {set s [socket 127.0.0.1 $port]} err]} {
    puts "RESULT connfail $err"
    exit 0
}
fconfigure $s -translation binary -blocking 0 -buffering none
set ::buf ""
set ::done 0
fileevent $s readable [list onread $s]
set t [after $ms {set ::done 1}]
vwait ::done
after cancel $t
catch {close $s}
set line [lindex [split $::buf "\n"] 0]
puts "RESULT ok banner=[string map {"\r" "" "\n" ""} $line]"