Windows 7 / Networking

Testing Service Connectivity

After you have identified the port number for the service, you can use Telnet Client to test connectivity to that service. To test connectivity to a service, open a command prompt and run the following command.

telnet destination portnumber

For example, to test HTTP connectivity to, type the following command at the command line.

telnet 80

The destination might be a host name, computer name, or IP address. The response you receive will indicate whether a connection was established. If you receive the message "Could not open connection to the host," the host did not respond to the request for a connection on the port number you specified, and the service you are testing is unreachable.

If you receive any other response, including all text disappearing from the command window, the connection was successfully established. This eliminates the possibility that the problem you are troubleshooting is caused by a connectivity issue between the client and the server. Depending on the service you are testing, Telnet Client can be automatically disconnected, or the session might remain open. Either circumstance indicates a successful connection. If the Telnet Client session remains open, you should disconnect Telnet Client to close the connection.

To disconnect Telnet Client, follow these steps:

  1. Press Ctrl+].
  2. When the Microsoft Telnet> prompt appears, type quit.
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In this tutorial:

  1. Troubleshooting Network Issues
  2. Tools for Troubleshooting
  3. Table-1 Network Troubleshooting Tools
  4. Arp
  5. How to Identify a Problem with the ARP Cacher
  6. How to Clear the ARP Cache
  7. Event Viewer
  8. IPConfig
  9. Nblookup
  10. Nbtstat
  11. Net
  12. How to View Shared Folders on the Local Computer
  13. How to View Shared Folders on Another Computer
  14. Netstat
  15. Network Monitor
  16. Nslookup
  17. Verifying that the Default DNS Server Resolves Correctly
  18. Verifying that a Specific DNS Server Resolves Correctly
  19. Verifying Specific Types of Addresses
  20. Using TCP for DNS Lookups
  21. PathPing
  22. PathPing Output
  23. Routing Loops
  24. Performance Problems
  25. Possible Connectivity Issues
  26. No Connectivity Issues
  27. Performance Monitor
  28. Data Collector Sets
  29. Windows Resource Monitor
  30. Ping
  31. PortQry
  32. Identifying the TCP Port for a Service
  33. Windows 7 Testing Service Connectivity
  34. Determining Available Remote Management Protocols
  35. Why PortQry Is Great
  36. Route
  37. Task Manager
  38. TCPView
  39. Telnet Client
  40. Testing Service Connectivity
  41. Test TCP
  42. Windows Network Diagnostics
  43. The Process of Troubleshooting Network Problems
  44. How to Troubleshoot Network Connectivity Problems
  45. How to Troubleshoot Application Connectivity Problems
  46. Default Port Assignments for Common Services and Tasks
  47. How to Troubleshoot Name Resolution Problems
  48. How to Verify Connectivity to a DNS Server
  49. How to Use the Hosts File
  50. How to Troubleshoot Performance Problems and Intermittent Connectivity Issues
  51. How to Troubleshoot Joining or Logging on to a Domain
  52. How to Verify Requirements for Joining a Domain
  53. How to Troubleshoot Network Discovery
  54. How to Troubleshoot File and Printer Sharing
  55. How to Troubleshoot File and Printer Sharing from the Client
  56. How to Troubleshoot File and Printer Sharing from the Server
  57. How to Troubleshoot Wireless Networks
  58. Network Diagnostics
  59. How to Troubleshoot Firewall Problems