Systemd service not behaving similar to manual ExecStart command run - service

Question

I have pcieserver.service in systemd enabled which triggers /opt/pcieserver/pcieserver.sh script, and it seems to work fine.
One problem I am facing is, this server reads a socket using nc(netcat) and dumps the data to /tmp/temp file; if I run this script using sudo /opt/pcieserver/pcieserver.sh command, and then trigger the nc to dump data, the temp file is created and data is dumped as expected. If I trigger the nc when it is running from systemd service, it generates the file, but there is no data being dumped i.e. stays 0kb always.
systemd service file placed under /etc/systemd/system/pcieserver.service
contents:
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=PCIe-Server
After=network.target
[Service]
Type=simple
ExecStart=/opt/pcieserver/pcieserver.sh
Restart=on-failure
RestartSec=30
[Install]
WantedBy=multi-user.target
pcieserver.sh contents:
# Getting Script Directory
SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
cd ${SCRIPT_DIR}
/usr/bin/sudo python ${SCRIPT_DIR}/pcieserver.py
journalctl output:
pcieserver.startLocalTrace[26859]: startLocalTrace function...
pcieserver.sh[26851]: 2018-12-24 06:57:38,169 startLocalTrace function...
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Delete local Trace:/tmp/trace
pcieserver.deleteLocalTrace[26859]: Delete local Trace:/tmp/trace
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Tracefile /tmp/trace exists, delete...
pcieserver.deleteLocalTrace[26859]: Tracefile /tmp/trace exists, delete...
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Tracefile /tmp/trace exists, delete...done
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Start local Trace to file /tmp/trace...
pcieserver.deleteLocalTrace[26859]: Tracefile /tmp/trace exists, delete...done
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Start local Trace to file /tmp/trace. Command:nc 127.0.0.1 4705 >/tmp/trace
pcieserver.sh[26851]: 2018-12-24 06:57:38,170 Start process:nc 127.0.0.1 4705 >/tmp/trace
pcieserver.startLocalTrace[26859]: Start local Trace to file /tmp/trace...
pcieserver.startLocalTrace[26859]: Start local Trace to file /tmp/trace. Command:nc 127.0.0.1 4705 >/tmp/trace
pcieserver.startProcess[26859]: Start process:nc 127.0.0.1 4705 >/tmp/trace
pcieserver.startLocalTrace[26859]: Start local Trace to file /tmp/trace...started
pcieserver.sh[26851]: 2018-12-24 06:57:38,176 Start local Trace to file /tmp/trace...started
sudo[4121]: root : TTY=unknown ; PWD=/opt/pcieserver ; USER=root ; COMMAND=/bin/nc 127.0.0.1 4705
sudo[4121]: pam_unix(sudo:session): session opened for user root by (uid=0)
P.S. I checked the permissions are same in both cases.