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Errors reported by CheckUpDown

Introduction to errors

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with your Web server:

  • Obtain an IP address from the IP name of your site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
  • Open an IP socket connection to that IP address.
  • Write an HTTP data stream through that socket.
  • Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

An error may occur in any of the above steps. Our CheckUpdown robot isolates any error and reports it as an error code for your account (as a clickable link) along with details of when the error was detected.

The error codes the client may receive are given below - follow the URL for each to see further discussion of the error and what further action we recommend.

0?? errors

Errors with a code in the range 001-099 indicate a fundamental failure to communicate, typically in the early steps above. Note these errors are not defined in the HTTP protocol - they are specific to our CheckUpDown service.

001 - Unknown Host
002 - I/O Exception
003 - Undefined HTTP Status Code
004 - Bad URL
005 - Host not reachable
006 - No connection
007 - I/O Interrupt
008 - Socket failure
009 - SSL secure socket failure
010 - Check word not found
011 - Socket Timeout

3?? errors

Errors with a code in the range 300-399 indicate a redirection of the Web site URL. As of September 2000, CheckUpDown follows some URL redirections (301, 302, 303, 307) automatically, so these should no longer be reported as an error.

300 - Multiple Choices
301 - Moved permanently
302 - Moved temporarily
303 - See other
304 - Not modified
305 - Use proxy
307 - Temporary Redirect

4?? errors

Errors with a code in the range 400-499 occur where the Web server - incorrectly or not - dislikes the HTTP data streams that the client sends to it. Quite rare.

400 - Bad request
401 - Unauthorized
403 - Forbidden
404 - Not found
405 - Method not allowed
406 - Not acceptable
407 - Proxy authentication required
408 - Request timeout
409 - Conflict
410 - Gone
411 - Length required
412 - Precondition failed
413 - Request entity too large
414 - Request URI too long
415 - Unsupported media type
416 - Requested Range not satisfiable
417 - Expectation failed

5?? errors

Errors with a code in the range 500-599 occur where the Web server reports an internal error in its operations.

500 - Internal server error
501 - Not implemented
502 - Bad gateway
503 - Service unavailable
504 - Gateway timeout
505 - HTTP version not supported