Dialog: Project Settings - Communication

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Dialog: Project Settings - Communication

Menu Tools > PROPERTIES Project Settings... | Communication


Communication Mode



Docklight acts both as transmitter and receiver of serial data. This mode is used when Testing the functionality or the protocol implementation of a serial device or simulating a serial device.

Naming conventions: The received data (RX) will be displayed and processed as "Channel 1", the transmitted data (TX) will be displayed as "Channel 2".



Docklight receives serial data on two different communication channels. This mode is used, for example, when Monitoring the communication between two devices.

Naming conventions: The serial data from device 1 is "Channel 1", the data from device 2 is "Channel 2".


Communication Channels - Serial COM ports, Docklight TAP/VTP, network TCP/UDP, HID, Named Pipes

In Docklight Scripting, a communication channel can be configured as

Serial COM port (RS232, RS422 or RS485),

TAP port for Docklight Tap monitoring

VTP port for Docklight Tap Pro or Tap 485 monitoring

Network communication socket for TCP or UDP

HID connections for USB or Bluetooth devices

Named Pipes client


The following settings can be used:


Setting / Examples






The channel is connected to a serial COM port.

Use the dropdown list to see all COM ports available on your PC from the Windows operating system.





The channel is connected to one of the Docklight Tap monitoring data directions. The TAP connections are only available if Communication Mode is set to 'Monitoring', the Docklight Tap is plugged in and the Docklight Tap USB device drivers are installed properly.





The channel is connected to one of the Tap Pro / Tap 485 monitoring data directions, similar to the Docklight Tap application using TAPx settings.




The channel acts a TCP client.

When starting communications, it connects to the host and TCP port specified. For RemoteHost you can enter

an IP4 address, e.g.

a host name, e.g. NIC.COM (for accessing a server on the Internet) or the Windows NetBIOS name for another computer on your local network.

the LOCALHOST keyword which always points to the computer Docklight is running on. This is equivalent to using the loopback IP address






The channel acts as a TCP server. When communication is started, Docklight accepts one connection from a TCP client. When a client is connected, further connection attempts are rejected.  




Same as SERVER, but in Monitoring Mode it will control the second channel according to the connection accepted by the server. If the second channel forcefully closes a connection, the PROXY server drops the accepted connection, too.






The channel acts as a UDP peer. Transmit data is sent to the destination RemoteHost:Port, and Docklight listens to UDP data on the local UDP port number Port.

When using a channel setting like UDP:LOCALHOST:10001 you effectively create a loopback, similar to a serial port loopback, where and all outgoing data is immediately received.





The channel acts as a UDP peer, but using different port numbers for outgoing and incoming data. Data is transmitted to RemotePort, and Docklight listens on the LocalPort.




The channel acts as a UDP server. Docklight listens for UDP data on LocalPort. Send data is transmitted to the source IP and port number of the last UDP packet received.




Client connection to a Named Pipe with read/write access

Client connection with read access only
Write access only





(or use USB Device Path)


USB HID input / output report

Docklight opens a connection to the specified USB HID device (or a Bluetooth HID device) and allows sending and receiving HID input and output report data.

The Docklight communication display is report-based: Each input report generates a new Docklight time stamp and prints the original HID report data, including the input report ID as the first byte, if > 0.





USB HID access, protocol based.

Only the actual payload data is displayed, without the leading Input Report ID byte and/or trailing zero bytes. Time stamps are generated according to the usual time stamp rules, not before every report.




USB HID access, but with variable output report ID as part of your Send Sequence data. In this mode, all Send Sequence definitions require an extra byte at the start of the sequence, which sets the actual Output Report ID to use.






USB HID extended syntax:

outputID: if specified, use this Output Report ID, instead of the default zero

outputPayloadSize: if specified, override the report length and ignore the value Windows reports via HID_CAPS.OutputReportByteLength




Client connection to a Named Pipe with read/write access

Client connection with read access only
Write access only


Monitoring Mode - Channel Combinations And Their Applications

In Monitoring Mode, two communication channels are available, which can be set up individually. This allows Docklight Scripting to be used in a large number of different applications and test environments. Below is a list of typical channel combinations:


Communication Channel Settings

Example Settings



Ch1: COM Port

Ch2: COM Port



Monitoring Serial Communications Between Two Devices using a Docklight Monitoring Cable

Ch1: Docklight Tap

Ch2: Docklight Tap



Monitoring Serial Communications Between Two Devices using a Docklight Tap

Ch1: Tap Pro or 485

Ch2: Tap Pro or 485



Monitoring Serial Communications Between Two Devices using a Docklight Tap Pro or Docklight Tap 485

Ch1: COM Port

Ch2: TCP Server



Emulating a Serial Device Server. A client can connect to the Docklight server on port 10001 and talk to the serial device connected on COM1.

Ch1: TCP Client

Ch2: TCP Server


Monitoring a Client/Server TCP Connection where Docklight acts as a gateway between the two sides.

Ch1: UDP Peer

Ch2: UDP Peer



Monitoring and forwarding a UDP transmission, similar to the TCP example above. Note that for each channel you need to specify a different UDP port, because each channel needs to listen on its own separate port number.



COM Port Settings (COM, TAP and VTP channels only)


Baud Rate

Choose a standard baud rate from the dropdown list, or use a non-standard baud rate by typing any integer number between 110 and 9999999.


NOTE: Non-standard baud rates may not work correctly on all COM ports, dependent on the capabilities of your COM port's hardware UART chip. You will receive no warning, if any non-standard rate cannot be applied.


NOTE: Although Docklight's Project Settings allow you to specify baud rates up to 9 MBaud, this does not mean Docklight is able to handle this level of throughput continuously. The average data throughput depends very much on your PC's performance and the Docklight display settings. See also How to Increase the Processing Speed.


NOTE: There are many COM ports drivers and applications that do not use actual RS232/422 or 485 transmission, and do not require any of the RS232 communication parameters. In some cases such COM port drivers even return an error when trying to set the RS232 parameters, so Docklight would fail to open the COM channel. Use the Baud Rate setting None for these applications.


Data Bits and Stop Bits

Specify the number of data bits and stop bits here. As with the baud rate, some of the available settings may not be supported by the COM port device(s) on your PC.


Tap 485 Sign. Level.

The Docklight Tap Pro / Tap 485 support additional voltage levels, besides the standard RS232 voltages:

RS485/422 - the differential voltage levels for RS485 and RS422 bus applications.

Inverted - Inverted RS232/TTL mode, where the mark state (or logical 1)  is the positive voltage, and the space state (logical 0) is the negative voltage or zero volts.



All common parity check options are available here. (The settings 'Mark' and 'Space' will probably not be used in practical applications. 'Mark' specifies that the parity bit always is 1, 'Space' that the parity bit is always 0, regardless of the character transmitted.)


Parity Error Character

This is the character that replaces an invalid character in the data stream whenever a parity error occurs. You should specify an ASCII character (printing or non-printing) that does not usually appear within your serial data stream. Characters may be defined by entering the character itself or entering its decimal ASCII code (please enter at least two digits).


NOTE: Choose "(ignore)" for the Parity Error Character if you need to transmit/receive the parity bit but Docklight should preserve all incoming characters, even when the parity bit is wrong. This is useful for applications where a 9th bit is used for addressing purposes and not for error checking.


Using Baud Rate Scan - VTP channels only


Docklight Tap Pro / Tap 485 devices offer a baud rate scan / autodetect mode. To activate baud rate scan, choose None from the Baud Rate setting and close the Project Settings dialog. Now start the communication using menu Run > play Start communication (F5). The Docklight Tap Pro / Tap 485 now scans the communication independently in both directions. If serial data could be detected in either data direction, the most probable settings are displayed as comments in the Communication Window. They are also are noted in the communications status bar under the main toolbar.


NOTE: The accuracy of this autodetection feature depends on the actual data stream present during the scan. A continuous stream of highly random data leads to high detection accuracy, while small transfers of individual bytes or repeating patterns may lead to wrong baud rates, data bit or parity guesses.