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diff --git a/lib/ping.rb b/lib/ping.rb
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+#
+# ping.rb -- check a host for upness
+#
+#= SYNOPSIS
+#
+#   require 'ping'
+#    print "'jimmy' is alive and kicking\n" if Ping.pingecho('jimmy', 10) ;
+#
+#= DESCRIPTION
+#
+# This module contains routines to test for the reachability of remote hosts.
+# Currently the only routine implemented is pingecho(). 
+#
+# pingecho() uses a TCP echo (I<not> an ICMP one) to determine if the
+# remote host is reachable. This is usually adequate to tell that a remote
+# host is available to rsh(1), ftp(1), or telnet(1) onto.
+#
+#== Parameters
+#
+#  : hostname
+#
+#    The remote host to check, specified either as a hostname or as an
+#    IP address.
+#
+#  : timeout
+#
+#    The timeout in seconds. If not specified it will default to 5 seconds.
+#
+#= WARNING
+#
+# pingecho() uses user-level thread to implement the timeout, so it may block
+# for long period if named does not respond for some reason.
+#
+#=end
+
+module Ping
+  require "socket"
+  def pingecho(host, timeout=5)
+    begin
+      x = Thread.current
+      y = Thread.start {
+	sleep timeout
+	x.raise RuntimeError if x.status
+      }
+      s = TCPsocket.new(host, "echo")
+      s.close
+      return TRUE
+    rescue
+      return FALSE;
+    ensure
+      Thread.kill y if y.status
+    end
+  end
+  module_function "pingecho"
+end