One think I forgot to mention:
Please let us know the results of your tests....this external check can be
used from the current v3.x and will probably become an internal check in v4
(probably doesn't mean it's sure!)
Dirk.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
Behalf Of Dirk Bulinckx
Sent: Thursday, 30 May, 2002 11:38 AM
To: [EMAIL PROTECTED]
Subject: [SA-list] Generic UDP port connection test (BETA)
chkUDP external UDP checker for Servers Alive
(http://www.woodstone.nu/soft/beta/setup_chkudp.exe)
chkUDP will try to determine if something is listening on a (remote) UDP
port.
By default chkUDP will first ping the host to see if the host is active or
not. If the host is active it will send a UDP frame (some services/daemons
like a syslog service/daemon will log this packet, in the case of a syslog
server that's because the protocol definition of syslog requires it to log
anything it gets on it's udp port).
chkUDP uses some commandlines to get it's parameters.
chkudp /host=host_name /port=port_number /timeout=timeout_in_seconds
(timeout part is "only" use for the UDP part, not for the ping nor for the
eventual name resolution)
By default chkUDP will ping the host checking the UDP part. This can be
disabled by adding /ping=N to the commandline.
chkUDP will return 1 if the UDP port is active.
chkUDP will return 0 if the UDP port is non-active.
chkUDP will return -999 if there is a problem with the parameters. (Servers
Alive will always show a return of -999 as down)
See the info below on why it could be that active ports are seen as
non-active.
Some info on why what we're doing to check if a UDP port is active is not
100% reliable:
"UDP Internet Control Message Protocol (ICMP) port unreachable scanning is
one of the few UDP scans. UDP is a connectionless protocol, so it's harder
to scan than TCP because UDP ports aren't required to respond to probes.
Most implementations generate an ICMP port unreachable error when a user (or
intruder) sends a packet to a closed UDP port. Thus, a lack of a response
indicates an active port. Unfortunately, UDP port scanning is not as
reliable as TCP port scanning. If you have a firewall between you and the
internet that blocks UDP traffic by simply dropping the packet, and sends no
response, our port scan will detect this as an indication of an open port."
Dirk.
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