iperf3 error :unable to read from stream socket: Resource temporarily unavailable

Precondition: created alias IP on eth0 for both server and client, both are using the same version of iperf3.

Server:
iperf3 -s -V -B 162.243.144.198

Client:
iperf3 -c 162.243.144.198 -B 192.168.163.1 -u -b 1M -i 1 -t 120 -J

Result:
`{
"start": {
"connected": [],
"version": "iperf 3.1.7",
"system_info": "Linux ams-gw-3 3.10.0-957.10.1.el7.x86_64 #1 SMP Mon Mar 18 15:06:45 UTC 2019 x86_64",
"timestamp": {
"time": "Mon, 29 Apr 2019 01:03:41 GMT",
"timesecs": 1556499821
},
"connecting_to": {
"host": "162.243.144.198",
"port": 5201
},
"cookie": "ams-gw-3.1556499821.535002.263807b47"
},
"intervals": [],
"end": {},
"error": "error - unable to read from stream socket: Resource temporarily unavailable"
}`

This is intermittent, some runs succeed in generating connection