Error Message

2010/08/03 10:17:23 VCS ERROR V-16-10061-3 RemoteGroup: :monitor:Error in connecting to the remote cluster (ip address ). VCS API call returned with Error Id 251 and Error Message: Failed to open socket connection to port 14141 on host
 

*** Using NMAP to test connectivity through a Firewall

During a normal TCP connection, the source initiates the connection by sending a SYN packet to a port on the destination system. If a service is listening on that port, the service responds with a SYN/ACK packet. The client initiating the connection then responds with an ACK packet, and the connection is established. If the destination host is not waiting for a connection on the specified port, it responds with an RST packet. Most system logs do not log completed connections until the final ACK packet is received from the source.

Sending other types of packets that do not follow this sequence can elicit useful responses from the target host, without causing a connection to be logged. This is known as a TCP half scan, or a stealth scan, because it does not generate a log entry on the scanned host.
But this type of scanning has its own merits and demerits as it is not effective against Microsoft Platform, and in fact whenever a FIN packet is send to any port it reply's with RST, but this can be used to discover that this system is Microsoft Based. On the other hand it works fine with *nix Boxes.

You can send several different type of packets to initiate various types of stealth scans, such as the following:

   * NULL scan
   * Christmas scan (SYN+FIN+ACK)
   * SYN-FIN scan



An example of this is :
         
#nmap -sN  -p  14141       <= This is Null Scan

#nmap -sX   -p 14141      <= This is Xmus Scan

#nmap -sF   -p 14141       <= This is FIN Scan
 

           .
*** output should look similar to this:

# nmap -sF 155.64.186.189 -p 14141

Starting Nmap 4.76 ( https://nmap.org ) at 2009-12-08 11:44 PST
Interesting ports on 155.64.186.189:
PORT      STATE         SERVICE
14141/tcp open|filtered unknown
MAC Address: 00:03:BA:12:6A:A4 (Sun Microsystems)

Nmap done: 1 IP address (1 host up) scanned in 7.27 seconds


Note:
If a port is blocked or not enabled it will report back as "closed"

This is a third-party application that might need to be installed on the system.