LightstreamerClient

A constant string representing the name of the library.

A constant string representing the version of the library.

Data object that contains the details needed to open a connection to a Lightstreamer Server. This instance is set up by the LightstreamerClient object at its own creation.
Properties of this object can be overwritten by values received from a Lightstreamer Server. Such changes will be notified through a ClientListener#onPropertyChange event on listeners of this instance.

Data object that contains options and policies for the connection to the server. This instance is set up by the LightstreamerClient object at its own creation.
Properties of this object can be overwritten by values received from a Lightstreamer Server. Such changes will be notified through a ClientListener#onPropertyChange event on listeners of this instance.

Static method that permits to configure the logging system used by the library. The logging system must respect the LoggerProvider interface. A custom class can be used to wrap any third-party JavaScript logging system.
A ready-made LoggerProvider implementation is available within the library in the form of the SimpleLoggerProvider class.
If no logging system is specified, all the generated log is discarded.
The following categories are available to be consumed:

• lightstreamer.stream:
  logs socket activity on Lightstreamer Server connections;
  at DEBUG level, read data is logged, write preparations are logged.
• lightstreamer.protocol:
  logs requests to Lightstreamer Server and Server answers;
  at DEBUG level, request details and events from the Server are logged.
• lightstreamer.session:
  logs Server Session lifecycle events;
  at INFO level, lifecycle events are logged;
  at DEBUG level, lifecycle event details are logged.
• lightstreamer.requests:
  logs submission of control requests to the Server;
  at WARN level, alert events from the Server are logged;
  at INFO level, submission of control requests is logged;
  at DEBUG level, requests batching and handling details are logged.
• lightstreamer.subscriptions:
  logs subscription requests and the related updates;
  at INFO level, subscriptions and unsubscriptions are logged;
  at DEBUG level, requests handling details are logged.
• lightstreamer.messages:
  logs sendMessage requests and the related updates;
  at INFO level, sendMessage operations are logged;
  at DEBUG level, request handling details are logged.
• lightstreamer.actions:
  logs settings / API calls.

Adds a listener that will receive events from the LightstreamerClient instance.
The same listener can be added to several different LightstreamerClient instances.

Lifecycle: a listener can be added at any time.

Operation method that requests to open a Session against the configured Lightstreamer Server.
When connect() is called, unless a single transport was forced through ConnectionOptions#setForcedTransport, the so called "Stream-Sense" mechanism is started: if the client does not receive any answer for some seconds from the streaming connection, then it will automatically open a polling connection.
A polling connection may also be opened if the environment is not suitable for a streaming connection.
When connect() is used to activate the Lightstreamer Session on page start up, it is suggested to make this call as the latest action of the scripts in the page. Otherwise, if the stream connection is opened but third-party scripts are consuming most of the CPU for page initialization (initial rendering, etc.), the parsing of the streaming response could be delayed to the point that the Client switches to polling mode. This is usually not the case nowadays but may still happen if the client is used on old machines.
Note that as "polling connection" we mean a loop of polling requests, each of which requires opening a synchronous (i.e. not streaming) connection to Lightstreamer Server.

Lifecycle: Note that the request to connect is accomplished by the client asynchronously; this means that an invocation to LightstreamerClient#getStatus right after connect() might not reflect the change yet. Also if a CPU consuming task is performed right after the call the connection will be delayed.
When the request to connect is finally being executed, if the current status of the client is not DISCONNECTED, then nothing will be done.

Operation method that requests to close the Session opened against the configured Lightstreamer Server (if any).
When disconnect() is called, the "Stream-Sense" mechanism is stopped.
Note that active Subscription instances, associated with this LightstreamerClient instance, are preserved to be re-subscribed to on future Sessions.

Lifecycle: Note that the request to disconnect is accomplished by the client asynchronously; this means that an invocation to LightstreamerClient#getStatus right after disconnect() might not reflect the change yet. Also if a CPU consuming task is performed right after the call the disconnection will be delayed.
When the request to disconnect is finally being executed, if the status of the client is "DISCONNECTED", then nothing will be done.

Inquiry method that returns the MpnSubscription with the specified subscription ID, or null if not found.
The object returned by this method can be an object created by the user, via MpnSubscription constructors, or an object created by the client, to represent pre-existing MPN subscriptions.
Note that objects returned by this method may be substitutued at any time with equivalent ones: do not rely on pointer matching, instead rely on the MpnSubscription#getSubscriptionId value to verify the equivalence of two MpnSubscription objects. Substitutions may happen when an MPN subscription is modified, or when it is coalesced with a pre-existing subscription.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Returns an array containing the ClientListener instances that were added to this client.

Inquiry method that returns a collection of the existing MPN subscription with a specified status.
Can return both objects created by the user, via MpnSubscription constructors, and objects created by the client, to represent pre-existing MPN subscriptions.
Note that objects in the collection may be substituted at any time with equivalent ones: do not rely on pointer matching, instead rely on the MpnSubscription#getSubscriptionId value to verify the equivalence of two MpnSubscription objects. Substitutions may happen when an MPN subscription is modified, or when it is coalesced with a pre-existing subscription.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Lifecycle: The collection is available once an MpnDevice registration has been requested, but reflects the actual server's collection only after an MpnDeviceListener#onSubscriptionsUpdated event has been notified.

Inquiry method that gets the current client status and transport (when applicable).

Inquiry method that returns an array containing all the Subscription instances that are currently "active" on this LightstreamerClient.
Internal second-level Subscription are not included.

Operation method that registers the MPN device on the server's MPN Module.
By registering an MPN device, the client enables MPN functionalities such as LightstreamerClient#subscribeMpn.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Lifecycle: An MpnDevice can be registered at any time. The registration will be notified through a MpnDeviceListener#onRegistered event.

Removes a listener from the LightstreamerClient instance so that it will not receive events anymore.

Lifecycle: a listener can be removed at any time.

Operation method that sends a message to the Server. The message is interpreted and handled by the Metadata Adapter associated to the current Session. This operation supports in-order guaranteed message delivery with automatic batching. In other words, messages are guaranteed to arrive exactly once and respecting the original order, whatever is the underlying transport (HTTP or WebSockets). Furthermore, high frequency messages are automatically batched, if necessary, to reduce network round trips.
Upon subsequent calls to the method, the sequential management of the involved messages is guaranteed. The ordering is determined by the order in which the calls to sendMessage are issued .
If a message, for any reason, doesn't reach the Server (this is possible with the HTTP transport), it will be resent; however, this may cause the subsequent messages to be delayed. For this reason, each message can specify a "delayTimeout", which is the longest time the message, after reaching the Server, can be kept waiting if one of more preceding messages haven't been received yet. If the "delayTimeout" expires, these preceding messages will be discarded; any discarded message will be notified to the listener through ClientMessageListener#onDiscarded. Note that, because of the parallel transport of the messages, if a zero or very low timeout is set for a message and the previous message was sent immediately before, it is possible that the latter gets discarded even if no communication issues occur. The Server may also enforce its own timeout on missing messages, to prevent keeping the subsequent messages for long time.
Sequence identifiers can also be associated with the messages. In this case, the sequential management is restricted to all subsets of messages with the same sequence identifier associated.
Notifications of the operation outcome can be received by supplying a suitable listener. The supplied listener is guaranteed to be eventually invoked; listeners associated with a sequence are guaranteed to be invoked sequentially.
The "UNORDERED_MESSAGES" sequence name has a special meaning. For such a sequence, immediate processing is guaranteed, while strict ordering and even sequentialization of the processing is not enforced. Likewise, strict ordering of the notifications is not enforced. However, messages that, for any reason, should fail to reach the Server whereas subsequent messages had succeeded, might still be discarded after a server-side timeout, in order to ensure that the listener eventually gets a notification.
Moreover, if "UNORDERED_MESSAGES" is used and no listener is supplied, a "fire and forget" scenario is assumed. In this case, no checks on missing, duplicated or overtaken messages are performed at all, so as to optimize the processing and allow the highest possible throughput.

Lifecycle: Since a message is handled by the Metadata Adapter associated to the current connection, a message can be sent only if a connection is currently active. If the special enqueueWhileDisconnected flag is specified it is possible to call the method at any time and the client will take care of sending the message as soon as a connection is available, otherwise, if the current status is "DISCONNECTED*", the message will be abandoned and the ClientMessageListener#onAbort event will be fired.
Note that, in any case, as soon as the status switches again to "DISCONNECTED*", any message still pending is aborted, including messages that were queued with the enqueueWhileDisconnected flag set to true.
Also note that forwarding of the message to the server is made asynchronously; this means that if a CPU consuming task is performed right after the call, the message will be delayed. Hence, if a message is sent while the connection is active, it could be aborted because of a subsequent disconnection. In the same way a message sent while the connection is not active might be sent because of a subsequent connection.

Operation method that adds a Subscription to the list of "active" Subscriptions. The Subscription cannot already be in the "active" state.
Active subscriptions are subscribed to through the server as soon as possible (i.e. as soon as there is a session available). Active Subscription are automatically persisted across different sessions as long as a related unsubscribe call is not issued.

Lifecycle: Subscriptions can be given to the LightstreamerClient at any time. Once done the Subscription immediately enters the "active" state.
Once "active", a Subscription instance cannot be provided again to a LightstreamerClient unless it is first removed from the "active" state through a call to LightstreamerClient#unsubscribe.
Also note that forwarding of the subscription to the server is made asynchronously; this means that if a CPU consuming task is performed right after the call the subscription will be delayed.
A successful subscription to the server will be notified through a SubscriptionListener#onSubscription event.

Operation method that subscribes an MpnSubscription on server's MPN Module.
This operation adds the MpnSubscription to the list of "active" subscriptions. MPN subscriptions are activated on the server as soon as possible (i.e. as soon as there is a session available and subsequently as soon as the MPN device registration succeeds). Differently than real-time subscriptions, MPN subscriptions are persisted on the server's MPN Module database and survive the session they were created on.
If the coalescing flag is set, the activation of two MPN subscriptions with the same Adapter Set, Data Adapter, Group, Schema and trigger expression will be considered the same MPN subscription. Activating two such subscriptions will result in the second activation modifying the first MpnSubscription (that could have been issued within a previous session). If the coalescing flag is not set, two activations are always considered different MPN subscriptions, whatever the Adapter Set, Data Adapter, Group, Schema and trigger expression are set.
The rationale behind the coalescing flag is to allow simple apps to always activate their MPN subscriptions when the app starts, without worrying if the same subscriptions have been activated before or not. In fact, since MPN subscriptions are persistent, if they are activated every time the app starts and the coalescing flag is not set, every activation is a new MPN subscription, leading to multiple push notifications for the same event.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Lifecycle: An MpnSubscription can be given to the LightstreamerClient once an MpnDevice registration has been requested. The MpnSubscription immediately enters the "active" state.
Once "active", an MpnSubscription instance cannot be provided again to an LightstreamerClient unless it is first removed from the "active" state through a call to #unsubscribeMpn.
A successful subscription to the server will be notified through an MpnSubscriptionListener#onSubscription event.

Operation method that removes a Subscription that is currently in the "active" state.
By bringing back a Subscription to the "inactive" state, the unsubscription from all its items is requested to Lightstreamer Server.

Lifecycle: Subscription can be unsubscribed from at any time. Once done the Subscription immediately exits the "active" state.
Note that forwarding of the unsubscription to the server is made asynchronously; this means that if a CPU consuming task is performed right after the call the unsubscription will be delayed.
The unsubscription will be notified through a SubscriptionListener#onUnsubscription event.

Operation method that unsubscribes an MpnSubscription from the server's MPN Module.
This operation removes the MpnSubscription from the list of "active" subscriptions.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Lifecycle: An MpnSubscription can be unsubscribed from at any time. Once done the MpnSubscription immediately exits the "active" state.
The unsubscription will be notified through an MpnSubscriptionListener#onUnsubscription event.

Operation method that unsubscribes all the MPN subscriptions with a specified status from the server's MPN Module.
By specifying a status filter it is possible to unsubscribe multiple MPN subscriptions at once. E.g. by passing TRIGGERED it is possible to unsubscribe all triggered MPN subscriptions. This operation removes the involved MPN subscriptions from the list of "active" subscriptions.

Edition Note: MPN is an optional feature, available depending on Edition and License Type. To know what features are enabled by your license, please see the License tab of the Monitoring Dashboard (by default, available at /dashboard).

Lifecycle: Multiple unsubscription can be requested at any time. Once done the involved MPN subscriptions immediately exit the "active" state.
The unsubscription will be notified through an MpnSubscriptionListener#onUnsubscription event to all involved MPN subscriptions.