5.9  Verify Status Codes

The response from a website to a request for a bookmark’s URL normally contains an HTTP Status Code, which is usually a positive integer between 100 and 599, although some creative cowboy webmasters sometimes return their own made-up status codes, usually in the range 600 to 999.

However, “lower level” errors can occur if the site does not send an HTTP response.  These lower level errors are returned to BookMacster by Mac OS X and contain “error codes” in Apple’s NSURLErrorDomain.  The codes in NSURLErrorDomain are negative numbers.

Fortunately (maybe because Apple planned it this way), there is no overlap between these positive and negative values.  Therefore, BookMacster stores in its Verify results for a bookmark what we call a Verify Status Code.  Quite simply, if this value is positive, it’s an HTTP Status Code, and if negative, it’s an error code in the NSURLErrorDomain.

5.9.1  Verify Status Codes for Positive Values (HTTP Status Codes)

Most of the HTTP status codes you will see are defined in Section 10 of Internet Society’s specification HTTP/1.1.  But although it was published in 1999, this document still has not been ratified into a standard, and in the meantime additional codes have been proposed.  For a readable and more complete table of the HTTP status codes in use at this time, we recommend this Wikipedia article.

5.9.2  Verify Status Codes for Negative Values (NSURLErrorDomain)

The following is derived from the file NSURLErrorDomain.h, but we’ve published them here since you will not have that file unless you have installed Apple’s Developer Tools, and also we added the narrative descriptions.