Testing port connectivity with Telnet-gctid50683

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Testing port connectivity with Telnet                                            http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003487
Purpose For  troubleshooting purposes, it may be necessary to test connectivity to  the different ports on your servers.  This article provides you with the  steps to use the Telnet utility to test connectivity to different ports  on your servers from either a Windows or Linux host.  
Resolution Testing port connectivity with Telnet from Windows Note: The  Telnet client is not installed by default on Windows 7, Windows Server  2008 R2, Windows Vista, and Windows Server 2008. For more information,  see http://technet.microsoft.com/en-us/library/cc771275(WS.10).aspx.
 
 The preceding link  was correct as of June 2, 2011. If you find the link is broken, provide  feedback and a VMware employee will update the link.
 
 To initiate a Telnet test to a port from Windows:
 
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• Open a command prompt. For more information, see Opening a command or shell prompt (1003892).
  
  
• In the command prompt window type:

telnet  

where  is the hostname or IP address of the server, and  is the port that you want to connect to.

• Press Enter.

Note: To exit out of the Telnet application  type Ctrl + ], then type quit.
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 Depending on the  application that uses the port, you may only see a blank screen with a  cursor in the corner, this is normal. Two common outputs of a successful  connection attempt are:
 
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• Connecting to port 902 on an ESX/ESXi host:

C:>telnet server 902
Connecting...

220 VMware Authentication Daemon Version 1.10: SSL Required, ServerDaemonProtocol:SOAP, MKSDisplayProtocol:VNC

• Connecting to port 25 on a mail server:

C:>telnet server 25
Connecting...

220 server ESMTP Sendmail 8.13.3/8.13.3;

• Connecting to port 443 on the vCenter Server:

C:>telnet server 443
Connecting...

220 VMware Authentication Daemon Version 1.10: SSL Required, ServerDaemonProtocol:SOAP, MKSDisplayProtocol:VNC
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 If Telnet is unable to connect to the port, the output is similar to:
 
 C:>telnet server 902
Connecting To server...
 
 Could not open connection to the host, on port 902: Connect failed
 
 C:>  
 Testing port connectivity with Telnet from Linux or MacOS To initiate a Telnet test to a port from Linux or MacOS:
 
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• Open a shell prompt. For more information, see Opening a command or shell prompt (1003892).
  
  
• In the shell prompt window type:

telnet  

where  is the hostname or IP address of the server, and  is the port that you want to connect to

• Press Enter.

Note: To exit out of the Telnet application  type CTRL + ], then type quit.
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 Depending on the  application that uses the port, you may only see a blank screen with a  cursor in the corner, this is normal. Two common outputs of a successful  connection attempt are:
 
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• Connecting to port 902 on an ESX/ESXi host:

[root@server]$ telnet server 902
Trying server...
Connected to server.
Escape character is '^]'.
220 VMware Authentication Daemon Version 1.10: SSL Required, ServerDaemonProtocol:SOAP, MKSDisplayProtocol:VNC


• Connecting to port 25 on a mail server:

[root@server]$ telnet server 25
Trying server...
Connected to server.
Escape character is '^]'.
220 server ESMTP Sendmail 8.13.3/8.13.3;
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 If Telnet is unable to connect to the port, the output is similar to:
 
 [root@server]$ telnet server 902
 Trying server...
telnet: connect to address server: Connection refused

If  the connection is refused, a firewall may be blocking that port from  your source to the destination server. For more information, see

Required ports for configuring an external firewall to allow ESX and vCenter Server traffic (1005189).    
 Note:  Several distributions of Linux do not have a Telnet client installed by  default. Refer to the website of your distribution for details on  whether one is available and how to install the package.
 
 Additional Information:
 
 For translated versions of this article, see:
 Portuguese Testando a conectividade de porta com Telnet (2015980)
 Spanish Prueba de conectividad de puertos con Telnet (2016367)
 
Additional Information For more information on required ports for VMware products, see TCP and UDP Ports required to access vCenter Server, ESX hosts, and other network components (1012382)
 
Tags  cannot-connect-esx cannot-connect-vm cannot-view-console  connect-guest-os guest-os misconfigured-firewall network-security  secure-network test-port-connectivity