WebSocketReceiver

Receives WebSocket messages from the specified WebSocket server.

Produces a feature each time a message is received, and places the contents of the message into the specified attribute. Each incoming feature will cause the WebSocketReceiver to initialize a connection to the specified WebSocket server. The transformer will block while it waits to receive WebSocket messages until the remote host closes the connection.

Usage Notes

The performance of this transformer is dependent on the amount of memory allocated to the Java Virtual Machine (JVM). The following environment variables allow you to specify memory available to Java Plugins:

FME_JVM_MIN_HEAP_SIZE: Initial heap size for initializing the JVM. If unset, the default value is 1024K.

These variables must be set in multiples of 1024 and greater than 1 MB. To indicate kilobytes, megabytes, or gigabytes, append k or K, m or M, or g or G respectively. For example, any of these values is acceptable:

6291456

6144k

FME_JVM_MAX_HEAP_SIZE: Maximum heap size for initializing the JVM. If unset, the default value is 16384K.

These variables must be set in multiples of 1024 and greater than 2 MB. To indicate kilobytes, megabytes, or gigabytes, append k or K, m or M, or g or G respectively. For example, any of these values is acceptable:

83886080

81920k

80m

Note: To pass additional parameters used by FME to the Java Virtual Machine, use the JAVA_TOOL_OPTIONS environment variable.

Configuration

Input Ports

Output Ports

Parameters

General

WebSocket Server URL

The URL of the remote WebSocket server that the WebSocketReceiver will connect to in order to receive WebSocket messages. The default value is ws://localhost:7078. To initiate a secure connection to a WebSocket server using TLS, specify wss://<hostname>:<port>.

Verify HTTPS Certificates

If Yes is specified, either explicitly or through a parameter, the WebSocketReceiver verifies the certificate (or chain of certificates) of the WebSocket server before establishing a connection.

Connection Preamble

If this optional parameter has a value, then the WebSocketReceiver will transmit the contents of this parameter to the remote WebSocket server before processing any incoming data.

To connect to the FME Flow WebSocket server, use the following preamble:

{

"ws_op" : "open",

"ws_stream_ids" : ["<STREAMID>", "<STREAMID>", "<STREAMID>", ...]

}

To specify this preamble, click the ellipsis (...) to open the Connection Preamble dialog. Under FME Flow WebSocket Preambles, select the Open Public Stream template. Then, specify a ws_stream_ids value.

ws_stream_ids identifies one or more message streams in order for the WebSocket server to associate them with the correct requesting application.

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

How to Set Parameter Values

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters	Create your own editable parameters.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Table Tools

Row Reordering

Enabled once you have clicked on a row item. Choices include:

Add a row
Remove a row
Move current row up one
Move current row down one
Move current row to top
Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

Cut a row - delete and copy to clipboard
Copy a row to the clipboard
Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

FME Community

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