A Receive TCP Message event trigger executes when a TCP message is received.
Defining a Receive TCP Message event trigger
To define a Receive TCP Message event trigger, follow these steps:
- From the Workbench left pane, expand the node where
you want to define the Receive TCP Message event
trigger.
- Select the Project icon to display
the Projects window, right-click a
specific project tab to display its pop-up menu, and
then select New.
You also can select the New button at the bottom of the Projects window when a specific project tab has already been selected. - The new Trigger window
appears.
Name the trigger. The trigger name can be up to 64 characters and include letters, numbers, and the underscore character. Spaces are allowed. - From the Event tab, select the
Trigger Event Type down-arrow, expand
the Networking category, and then
select Receive TCP Message.
The Event tab becomes active with parameters that accommodate the Receive TCP Message event.
| Parameter | Description |
|---|---|
| Device Name | The TCP Listener device that supports the TCP connection that receives TCP messages from partner applications. |
| Reply Format | The data format of an optional reply message. |
Receive TCP Message event type trigger event variables
The input event variables available to a Receive TCP Message event trigger are:
| Event variable | Data type | Description |
|---|---|---|
| Data | Based on the option selected for the Incoming Data Format parameter in the TCP Listener device. | The data received by the TCP Listener device. |
| Data Length | UINT4 | The size of the TCP data received by the TCP Listener device. |
| Device Name | STRING | The name of the TCP Listener device. |
| Source Address | STRING | The IP Address:port that the data was received from. |
| Label | STRING | If the TCP Listener device, Listener Type parameter is set to Active, the connection that the data was received from may have an optional label associated with it. |
| Label Populated | Boolean | Indicates if the Label event variable is populated |
The output event variables available to a Receive TCP Message event trigger are:
| Event variable | Data Type | Description |
|---|---|---|
| Reply Data | Based on the Reply Format parameter selection type. | Optional field present if the Reply
Format property is set to any option
other than None.
If set, the Reply Data will be sent over the connection that received the original TCP message. |
Receive TCP Message event trigger considerations
- The selected TCP Listener device must be Started for the Receive TCP Message event trigger to receive data.
- The TCP message handling behavior (fixed message length, variable message length with terminating characters, defined message header) is defined in the TCP Listener device Message Type parameter.
- Multiple Receive TCP Message event triggers can
be defined and started referencing the same TCP
Listener device.
Each trigger will receive a copy of the TCP message received by the TCP Listener device. - If multiple sending partner applications are sending TCP messages to the same IP address and port, then each sent TCP message will be received as a separate and distinct Receive TCP Message event trigger execution. The trigger execution behavior is based on the trigger settings for Max in Progress and Queue Size.
- The TCP driver and the TCP Listener device supports sending data back to the partner TCP application that sent the TCP message, through the Reply Data event variable.