Kbase 17605: How to Test Connectivity and Network Port Availability with Firewalls?
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
16/10/2008 |
|
Status: Unverified
GOAL:
How to Test Connectivity and Network Port Availability with Firewalls?
FIX:
Such tests are particularly useful if the listening machine is on the other side of a firewall from the machine that requests a connection. For example, a Progress WebSpeed messenger that communicates to a WebSpeed broker on another machine, or a Progress client that communicates in client/server mode to a database on another machine.
One way to test the availability of a port is to attempt a telnet connection from the requesting machine to the listening machine on the port in question. If the port is accessible and listening, you should get a connection. If not, the connection is refused.
NOTE: A successful test only results in a connection,
not an actual telnet session.
For example, to test the availability of port 3000 on listening machine "alpha" from the requesting machine use the command:
telnet alpha 3000
If the port is available and listening, you should see something like the following message:
Connected to alpha.
Escape character is '^]'.
This tells you that there is indeed a process on alpha that is listening for a connection on port 3000 and there is no external obstruction to this connection (a firewall, for example).
On the other hand, if you get a message like:
telnet: Unable to connect to remote host: Connection
refused
it means that port 3000 on alpha is inaccessible from the requesting machine. Perhaps there is no process listening on that port, or your connection is being obstructed by a firewall.
If you get an unable to connect message, the following
troubleshooting techniques can help you try to correct the problem:
1) Be sure the listening process is running.
For example, be sure there is a Progress broker or WebSpeed
broker running on the listening machine.
2) Be sure the listening process is running on the port you think
it is running on.
For a Progress database connection, check the Services file
to determine what port is associated with the service name
that is specified by the -S parameter when the database
broker started.
For WebSpeed, check the broker port that is specified in the
WebSpeed Configuration Utility (Windows NT) or the
webspeed.cnf file (UNIX).
3) Try a "local loopback" connection.
This means try the telnet test on the listening machine. In
our example, this means you must issue the telnet command
from alpha, to alpha.
If you get a connection, a process is listening on the
specified port but there must be some external obstruction
that prevents the connection from the other machine (most
likely a firewall).
4) Be sure your firewall is configured to allow connections on
the specified port.
You Probably have to check with your network or firewall
administrator.