I had to make these modifications to get it to work:
[Unit]
Description=Multipurpose relay (SOcket CAT)
After=network.target
**StartLimitIntervalSec=0**
**StartLimitBurst=3000**
[Service]
**Restart=always**
**RestartSec=3**
EnvironmentFile=/etc/default/socat-%i.conf
Type=simple
PIDFile=/var/run/socat-%i.pid
ExecStart=/usr/bin/socat -L/var/run/socat-%i.pid $SOCAT_DEFAULTS $SOCAT_CONNECTION
ExecStop=/bin/kill -SIGKILL $MAINPID
[Install]
WantedBy=multi-user.target
NOTE: Remove **
This is what the netstat looks like:
tcp 0 0 openHAB2-IP:35514 Z-WAVE-Controller-IP:3333 ESTABLISHED 2133/socat
<reboot z-wave controller>
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 1 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 SYN_SENT 2192/socat
tcp 0 0 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 ESTABLISHED 2192/socat
tcp 0 0 openHAB2-IP:35521 Z-WAVE-Controller-IP:3333 ESTABLISHED 2192/socat