Postgres intermittent connection errors: psql.bin: could not connect to server: Cannot assign requested address

Hi All,

We are receiving below intermittent connection error during performance testing on postgres.
Thanks in advance for any suggestion or pointers on how we can troubleshoot this issue.

Error: psql.bin: could not connect to server: Cannot assign requested address
Is the server running on host "abchost.corp.xyz.com" (xxx.xxx.xxx.xxx) and accepting
TCP/IP connections on port 5432?

Our organization is evaluating the feasibility of using postgres for an upcoming project.
As part of the evaluation we are performing a 50 concurrent user read performance testing.
Jmeter is the tool we are using for orchestrating the tests. It executes a shell script on 50 concurrent threads.

The shell script does the following:

a) Connects to postgres database server using psql.

b) Issues a single select statement on table with 200 rows .

c) Writes the results to a text file.

Jmeter client and database host are sitting in the same data center.
Database OS: RedHat 6.x,
DB Version: Postgres 9.6
Database is of decent config. 16 CPU, 64GB RAM, SAN storage.

Our tests are run for 10 to 15min.
During the middle of the run, we are noticing connection errors intermittently. (Around 20% calls are failing due to this).

While some calls are failing with the error: psql.bin: could not connect to server: Cannot assign requested address
Other calls are successful around the same timeframe may be one to two seconds later..

For the failed calls we are not able to see anything printed in the database server logs, (The exception is received on the client side).
For successful calls we are able to see the details of the sql statements, user, hostname etc... printed in the logs.

We have verified CPU,Memory,No of open files, netstat connection waits, but could not identify anything concrete that could be causing this issue.
The database is setup to accept 500 concurrent open connections and we are not using anywhere close to it.

Regards,
Vamsi