Operating system configuration (UNIX only)
IP validation depends on the system call getaddrinfo() to look up all the valid addresses for a host. The behavior of this routine varies, depending on the system configuration. When getaddrinfo() uses the file /etc/hosts, it returns the first matching entry. If the connection is initiated on an address which appears after the first matching entry, IP validation fails. To resolve the problem, place the entry used to initiate the connection before any other matching entries in the /etc/hosts file. If getaddrinfo() uses the "named" name server or the Network Information Service server and getaddrinfo() fails, contact your system administrator for assistance.