011 - Socket timeout


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

  1. Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
  2. Open an IP socket connection to that IP address.
  3. Write an HTTP data stream through that socket.
  4. 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.

This error occurs in the second step above. The connection to the server hosting the URL fails.

Resolving 011 errors

An inability to connect to the URL can be for any number of reasons. Firstly the machine hosting the Web server may be unreachable e.g. an intermediate router or firewall has failed. Secondly the Web server hosting the URL may be unreachable e.g. the Web service is down for some reason. Thirdly the Web server may be up, but not able to create a usable socket in time (within about 20 seconds) e.g. the server is simply overloaded.

There is no simple remedy. Technical support people at the site hosting the URL have to look at all the hardware/software required to run the Web service and figure out which bit is failing or simply running too slow. The 20 second limit we set for the creation of a usable socket is generous - most Web browser users give up on the URL (e.g. surf away to another site) long before 20 seconds have elapsed.