The segments access gpfdist at runtime. Ensure that the Greenplum segment hosts have network access to gpfdist. gpfdist is a web server: test connectivity by running the following command from each host in the Greenplum array (segments and master):
$ wget http://gpfdist_hostname:port/filename
The CREATE EXTERNAL TABLE definition must have the correct host name, port, and file names for gpfdist. Specify file names and paths relative to the directory from which gpfdist serves files (the directory path specified when gpfdist started). See Creating External Tables - Examples.
If you start gpfdist on your system and IPv6 networking is disabled, gpfdist displays this warning message when testing for an IPv6 port.
[WRN gpfdist.c:2050] Creating the socket failed
If the corresponding IPv4 port is available, gpfdist uses that port and the warning for IPv6 port can be ignored. To see information about the ports that gpfdist tests, use the -V option.
For information about IPv6 and IPv4 networking, see your operating system documentation.