ServerSentEvent Rust Reference Documentation

ServerSentEvent

Current Version: 11.6.1

Chilkat.ServerSentEvent

Parse server-sent event text into event name, data, ID, and retry fields.

Chilkat.ServerSentEvent is a small helper class for parsing Server-Sent Events formatted text. Given a multi-line event block, it extracts the event name, data payload, id value, and retry interval into simple read-only properties. It is useful when an application receives event-stream text and needs to work with the structured event fields instead of manually parsing the raw lines.

Load event text

Use LoadEvent to parse a complete multi-line Server-Sent Event block.

Read event name

Inspect EventName to determine the event type supplied by the server, if an event: field is present.

Read event data

Use Data to obtain the event payload, such as JSON text from a streaming API or real-time service.

Track event IDs

Read LastEventId when the event includes an id: field that identifies the event or stream position.

Handle retry hints

Use Retry to read the server-provided retry interval when a retry: field is included.

Diagnostics

Check LastErrorText if event text cannot be parsed or if a parsing result is unexpected.

Relationship to Chilkat.WebSocket: ServerSentEvent does not manage a WebSocket connection or parse WebSocket frames. Instead, it can be used after Chilkat.WebSocket receives a text message whose payload is formatted as a Server-Sent Event. Read the WebSocket text frame, pass the event text to LoadEvent, then use EventName, Data, LastEventId, and Retry to process the event.
Common pattern: Receive or otherwise obtain a complete Server-Sent Event text block, call LoadEvent, then inspect EventName to route the event and Data to process the payload. Use LastEventId and Retry when the stream provides reconnection or event-position information.

Object Creation

// Cargo.toml:
//     [dependencies]
//     chilkat = "11.6"

use chilkat::ServerSentEvent;

// Once per process, before any other Chilkat call:
chilkat::unlock_bundle("Anything for 30-day trial")?;  // shorthand for Global::new().unlock_bundle(..)

let server_sent_event = ServerSentEvent::new();
// ... the native object is freed when `server_sent_event` goes out of scope.
pub fn new() -> ServerSentEvent

Creates the underlying native Chilkat object (ServerSentEvent also implements Default). Every method takes &self, so the object never needs to be declared mut. A ServerSentEvent is Send but not Sync: it may be moved to another thread, but a reference to it cannot be shared between threads at the same time.

impl Drop for ServerSentEvent

The native object is freed when the ServerSentEvent is dropped — when it goes out of scope, or explicitly with drop(server_sent_event). There is no Dispose method to call.

Errors

Methods that can fail return chilkat::Result<T>, which is Result<T, chilkat::Error>: a method whose only outcome is success or failure returns Result<()>, a method producing a string or an object returns Result<String> or Result<ServerSentEvent>. The error carries the object's LastErrorText at the time of the failure (Error::last_error_text), the class and method names, and implements std::error::Error, so ? works in any function returning chilkat::Result or a Box<dyn Error>. Properties never fail, and methods that answer a question (has_..., is_..., ...) return a plain bool.

match server_sent_event.some_method(...) {
    Ok(value) => println!("{value:?}"),
    Err(e) => eprintln!("{}", e.last_error_text()),
}

Properties

Data
// read-only
pub fn data(&self) -> String
Introduced in version 9.5.0.58

The data for the server-side event. (If the data field was empty, then this will be empty.)

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DebugLogFilePath
// read/write
pub fn debug_log_file_path(&self) -> String
pub fn set_debug_log_file_path(&self, value: &str)

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

More Information and Examples
Example showing how to use DebugLogFilePath.
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EventName
// read-only
pub fn event_name(&self) -> String
Introduced in version 9.5.0.58

The name of the server-side event. (If the event field was not present, then this will be empty.)

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LastErrorHtml
// read-only
pub fn last_error_html(&self) -> String

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
// read-only
pub fn last_error_text(&self) -> String

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

More Information and Examples
Concept of LastErrorTextLastErrorText Standard Information
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LastErrorXml
// read-only
pub fn last_error_xml(&self) -> String

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastEventId
// read-only
pub fn last_event_id(&self) -> String
Introduced in version 9.5.0.58

The content of the id field, if present.

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LastMethodSuccess
// read/write
pub fn last_method_success(&self) -> bool
pub fn set_last_method_success(&self, value: bool)

Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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Retry
// read-only
pub fn retry(&self) -> i32
Introduced in version 9.5.0.58

The integer value of the retry field, if it exists; otherwise, 0.

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VerboseLogging
// read/write
pub fn verbose_logging(&self) -> bool
pub fn set_verbose_logging(&self, value: bool)

If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
// read-only
pub fn version(&self) -> String

Version of the component/library, such as "10.1.0"

More Information and Examples
How to get the Chilkat version at runtime.
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Methods

LoadEvent
pub fn load_event(&self, event_text: &str) -> Result<()>
Introduced in version 9.5.0.58

Loads the multi-line event text into this object. For example, the event_text for a Firebase event might look like this: 

event: put
data: {"path": "/c", "data": {"foo": true, "bar": false}}

Returns Ok(()) for success, Err(chilkat::Error) for failure.

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