Elfin EW11 TCP Client does not send data - tcpclient

Question

I want to use an Elfin EW11 device as a Modbus TCP Client/Master to send requests to a Modbus TCP Server/Slave (another Elfin EW11). It is connected via RS485 to my Test-Computer/PC.
PC ---RS485--> Elfin EW11 TCP Client ---WLAN---> Elfin EW11 TCP Server---RS485--->IOT Device
The Elfin EW11 Modbus TCP Client should reveive requests from ts RS485 Interface and send them via WLAN to the Modbus TCP Server.
It appears in its status-page, that
it is connected to the server
2, receives requests from RS485, but
does not send anything to the server
See screenshot of the status page of the Modbus TCP Client
Screenshot1
I already tried
a. the Modbus TCP server. It responds well when queried directly from my PC via WLAN
b. several options,timeouts etc. in the configuration of the TCP Client. Without success.
No data were transmitted from the TCP Client to the TCP Server
I would have expected at least that some bytes were transferred, even if the Modbus request would be wrong.
INSERT: I am quite sure that the frames/modbus requests sent from my PC are in the correct format (See my comments below)
Anyone got an Elfin EW11 working as a Modbus TCP Client?
My Client Config (backup XML):
<!--SYS Config-->
<SYS key='User' value='admin'>
<SYS key='Password' value='admin'>
<SYS key='DHCP' value='Enable'>
<SYS key='Ip Address' value='10.10.100.10'>
<SYS key='GateWay' value='10.10.100.254'>
<SYS key='Mask' value='255.255.255.0'>
<SYS key='Host Name' value='EW11-DTU'>
<SYS key='DNS' value='223.5.5.5'>
<SYS key='Telnet' value='Disable'>
<SYS key='Telnet Port' value='23'>
<SYS key='Echo' value='Enable'>
<SYS key='Web' value='Enable'>
<SYS key='Web Port' value='80'>
<SYS key='Ipv6' value='Disable'>
<SYS key='Ipv6 address' value=''>
<SYS key='Ipv6 DHCP' value='Disable'>
<SYS key='NTP' value='Disable'>
<SYS key='NTP Server' value=''>
<SYS key='NTP Port' value='0'>
<SYS key='NTP GMT' value='8'>
<SYS key='Customer ID' value='EW11'>
<SYS key='Config Version' value='0'>
<SYS key='NetworkMode' value='Router'>
<SYS key='WiFiMode' value='APSTA'>
<SYS key='WiFiAPSSID' value='EW11_F330'>
<SYS key='WiFiAPKey' value=''>
<SYS key='WiFiSTASSID' value='myWLAN'>
<SYS key='WiFiSTAKey' value='xxxxxxxxxx'>
<SYS key='WiFiAPCH' value='0'>
<SYS key='WiFiHideSSID' value='0'>
<SYS key='WiFiRoamingEn' value='0'>
<SYS key='ScanRSSIThreshold' value='0'>
<SYS key='ConnectRSSIThreshold' value='0'>
<SYS key='LanIpAddress' value='10.10.100.254'>
<SYS key='LanMarsk' value='255.255.255.0'>
<SYS key='LanDhcpEn' value='Enable'>
<SYS key='EthernetMode' value='WAN'>
<SYS key='Longitude' value='0.000000'>
<SYS key='Latitude' value='0.000000'>
<SYS key='SmartConfig' value='SmartLink'>
<SYS key='ModbusTime' value='0'>
<!--UART Config-->
<UART key='Baudrate' value='9600'>
<UART key='Databits' value='8'>
<UART key='Stopbits' value='1'>
<UART key='Parity' value='NONE'>
<UART key='FlowCtrl' value='Half-Duplex'>
<UART key='Software FlowCtrl' value='Disable'>
<UART key='Xon' value='11'>
<UART key='Xoff' value='13'>
<UART key='Protocol' value='Modbus'>
<UART key='Frame Length' value='16'>
<UART key='Frame Time' value='100'>
<UART key='Tag Enable' value='Disable'>
<UART key='Tag Head' value='00'>
<UART key='Tag Tail' value='00'>
<UART key='Buffer Size' value='512'>
<UART key='gapTime Size' value='50'>
<UART key='cliGetin' value='1'>
<UART key='serialStr' value='+++'>
<UART key='waitTime' value='300'>
<!--SOCK Config-->
<SOCK name='netp' key='Name' value='netp'>
<SOCK name='netp' key='Protocol' value='TCP-CLIENT'>
<SOCK name='netp' key='Server Addr' value='10.0.0.2'>
<SOCK name='netp' key='Remote Port' value='502'>
<SOCK name='netp' key='Local Port' value='0'>
<SOCK name='netp' key='Buffer Size' value='8192'>
<SOCK name='netp' key='KeepAlive' value='32'>
<SOCK name='netp' key='Timeout' value='60'>
<SOCK name='netp' key='Security' value='NONE'>
<SOCK name='netp' key='HeartBeat' value='Disable'>
<SOCK name='netp' key='Regist Mode' value='Disable'>
<SOCK name='netp' key='Regist Code' value=''>
<SOCK name='netp' key='Connect Mode' value='Always'>
<SOCK name='netp' key='VcomEn' value='0'>
<SOCK name='netp' key='Rout' value='uart'>
<!--CRC Config-->
<CRC key='CheckNum' value='231438'>
Server Config:
<!--SYS Config-->
<SYS key='User' value='admin'>
<SYS key='Password' value='admin'>
<SYS key='DHCP' value='Enable'>
<SYS key='Ip Address' value='10.10.100.10'>
<SYS key='GateWay' value='10.10.100.254'>
<SYS key='Mask' value='255.255.255.0'>
<SYS key='Host Name' value='EW11-DTSU666-H'>
<SYS key='DNS' value='223.5.5.5'>
<SYS key='Telnet' value='Disable'>
<SYS key='Telnet Port' value='23'>
<SYS key='Echo' value='Enable'>
<SYS key='Web' value='Enable'>
<SYS key='Web Port' value='80'>
<SYS key='Ipv6' value='Disable'>
<SYS key='Ipv6 address' value=''>
<SYS key='Ipv6 DHCP' value='Disable'>
<SYS key='NTP' value='Disable'>
<SYS key='NTP Server' value=''>
<SYS key='NTP Port' value='0'>
<SYS key='NTP GMT' value='8'>
<SYS key='Customer ID' value='EW11'>
<SYS key='Config Version' value='0'>
<SYS key='NetworkMode' value='Router'>
<SYS key='WiFiMode' value='STA'>
<SYS key='WiFiAPSSID' value='EW11_F0FC'>
<SYS key='WiFiAPKey' value=''>
<SYS key='WiFiSTASSID' value='myWLAN'>
<SYS key='WiFiSTAKey' value='xxxxxxxx'>
<SYS key='WiFiAPCH' value='0'>
<SYS key='WiFiHideSSID' value='0'>
<SYS key='WiFiRoamingEn' value='0'>
<SYS key='ScanRSSIThreshold' value='0'>
<SYS key='ConnectRSSIThreshold' value='0'>
<SYS key='LanIpAddress' value='10.0.0.2'>
<SYS key='LanMarsk' value='255.255.255.0'>
<SYS key='LanDhcpEn' value='Enable'>
<SYS key='EthernetMode' value='WAN'>
<SYS key='Longitude' value='0.000000'>
<SYS key='Latitude' value='0.000000'>
<SYS key='SmartConfig' value='SmartLink'>
<SYS key='ModbusTime' value='0'>
<!--UART Config-->
<UART key='Baudrate' value='9600'>
<UART key='Databits' value='8'>
<UART key='Stopbits' value='1'>
<UART key='Parity' value='NONE'>
<UART key='FlowCtrl' value='Half-Duplex'>
<UART key='Software FlowCtrl' value='Disable'>
<UART key='Xon' value='11'>
<UART key='Xoff' value='13'>
<UART key='Protocol' value='Modbus'>
<UART key='Frame Length' value='16'>
<UART key='Frame Time' value='100'>
<UART key='Tag Enable' value='Disable'>
<UART key='Tag Head' value='00'>
<UART key='Tag Tail' value='00'>
<UART key='Buffer Size' value='512'>
<UART key='gapTime Size' value='50'>
<UART key='cliGetin' value='1'>
<UART key='serialStr' value='+++'>
<UART key='waitTime' value='300'>
<!--SOCK Config-->
<SOCK name='netp' key='Name' value='netp'>
<SOCK name='netp' key='Protocol' value='TCP-SERVER'>
<SOCK name='netp' key='Server Addr' value='0.0.0.0'>
<SOCK name='netp' key='Remote Port' value='0'>
<SOCK name='netp' key='Local Port' value='502'>
<SOCK name='netp' key='Buffer Size' value='8192'>
<SOCK name='netp' key='KeepAlive' value='32'>
<SOCK name='netp' key='Timeout' value='600'>
<SOCK name='netp' key='Security' value='NONE'>
<SOCK name='netp' key='Connect Mode' value='Always'>
<SOCK name='netp' key='VcomEn' value='0'>
<SOCK name='netp' key='Rout' value='uart'>
<SOCK name='netp' key='maxAccept' value='3'>
<!--CRC Config-->
<CRC key='CheckNum' value='222713'>