requests that were made turned out no data.  Error handling
          code should be prepared to handle it when it is defined.

     EAI_SERVICE
          SERVICE was not recognized for the specified socket type.

     EAI_SOCKTYPE
          HINT_SOCKTYPE was not recognized.

     EAI_SYSTEM
          A system error occurred.  In C, the error code can be found in
          `errno'; this value is not accessible from Scheme, but in
          practice it provides little information about the actual error
          cause.

     Users are encouraged to read the POSIX specification
     (http://www.opengroup.org/onlinepubs/9699919799/functions/getaddrin
     fo.html) for more details.