# Could not connect to serial port from Windows

**URL:** <https://community.openhab.org/t/could-not-connect-to-serial-port-from-windows/43433>\
**Category:** Beginners\
**Tags:** windows, modbus\
**Created:** [April 10, 2018, 8:06am UTC](https://community.openhab.org/t/could-not-connect-to-serial-port-from-windows/43433 "2018-04-10T08:06:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![akcom](https://community.openhab.org/user_avatar/community.openhab.org/akcom/32/73290_2.png) [@akcom](https://community.openhab.org/u/akcom)\
**Post date:** [April 10, 2018, 8:06am UTC](https://community.openhab.org/t/could-not-connect-to-serial-port-from-windows/43433/1 "2018-04-10T08:06:18Z")

</div>

Hi, please help.  
I am newbie in OpenHab and am trying connect to the serial port on windows using modbus binding.

Here is my conf:  
serial.slave1.connection=“COM4”  
serial.slave1.id=“1”  
serial.slave1.length=“4”  
serial.slave1.start=“0”  
serial.slave1.type=“coil”

And here is error from logs:  
[ERROR] [pi.modbus.io.ModbusSerialTransaction] - execute try 1/3 error: readResponse I/O exception - failed to read: readResponse: I/O exception - Serial port timeout.. Request: net.wimpi.modbus.msg.ReadCoilsRequest@6e5f8669 (unit id 1 & transaction 889). Serial parameters: SerialParameters@7bec4c4b[portName=COM4,baudRate=9600,flowControlIn=none,flowControlOut=none,databits=8,stopbits=1,parity=none,encoding=ascii,echo=false,receiveTimeoutMillis=1500]

Versions:  
OpenHab 2  
Modbus binding 1.10.0  
Windows 8.1

COM4 is exists and successfully tested from another program (connection not locked).

---

<div class="post-metadata">

**Author:** ![sihui](https://community.openhab.org/user_avatar/community.openhab.org/sihui/32/55674_2.png) [@sihui](https://community.openhab.org/u/sihui)\
**Post date:** [April 10, 2018, 9:53am UTC](https://community.openhab.org/t/could-not-connect-to-serial-port-from-windows/43433/2 "2018-04-10T09:53:21Z")

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Make sure you have met all prerequisites:  
[https://docs.openhab.org/installation/windows.html](https://docs.openhab.org/installation/windows.html)

and double check your config in the modbus docs:  
[https://docs.openhab.org/addons/bindings/modbus1/readme.html](https://docs.openhab.org/addons/bindings/modbus1/readme.html)