Class WsRemoteEndpointImplServer

java.lang.Object
org.apache.tomcat.websocket.WsRemoteEndpointImplBase
org.apache.tomcat.websocket.server.WsRemoteEndpointImplServer
All Implemented Interfaces:
RemoteEndpoint
public class WsRemoteEndpointImplServer extends WsRemoteEndpointImplBase
This is the server side RemoteEndpoint implementation - i.e. what the server uses to send data to the client.

  • Constructor Details

    • WsRemoteEndpointImplServer

      public WsRemoteEndpointImplServer(SocketWrapperBase<?> socketWrapper, UpgradeInfo upgradeInfo, WsServerContainer serverContainer, WebConnection connection)
      Constructs a server-side remote endpoint.
      Parameters:
      socketWrapper - the socket wrapper
      upgradeInfo - the upgrade information
      serverContainer - the server container
      connection - the web connection

  • Method Details

    • isMasked

      protected final boolean isMasked()
      Description copied from class: WsRemoteEndpointImplBase
      Checks if frames should be masked.
      Specified by:
      isMasked in class WsRemoteEndpointImplBase
      Returns:
      true if masking is required

    • acquireMessagePartInProgressSemaphore

      protected boolean acquireMessagePartInProgressSemaphore(byte opCode, long timeoutExpiry) throws InterruptedException
      Acquire the semaphore that allows a message part to be written.

      The close message is a special case. It needs to be blocking else implementing the clean-up that follows the sending of the close message gets a lot more complicated. On the server, this creates additional complications as a deadlock may occur in the following scenario:

      1. Application thread writes message using non-blocking
      2. Write does not complete (write logic holds message pending lock)
      3. Socket is added to poller (or equivalent) for write
      4. Client sends close message
      5. Container processes received close message and tries to send close message in response
      6. Container holds socket lock and is blocked waiting for message pending lock
      7. Poller fires write possible event for socket
      8. Container tries to process write possible event but is blocked waiting for socket lock
      9. Processing of the WebSocket connection is deadlocked until the original message write times out
      The purpose of this method is to break the above deadlock. It does this by returning control of the processor to the socket wrapper and releasing the socket lock while waiting for the pending message write to complete. Normally, that would be a terrible idea as it creates the possibility that the processor is returned to the pool more than once under various error conditions. In this instance it is safe because these are upgrade processors (isUpgrade() returns true) and upgrade processors are never pooled.

      TODO: Despite the complications it creates, it would be worth exploring the possibility of processing a received close frame in a non-blocking manner.

      Overrides:
      acquireMessagePartInProgressSemaphore in class WsRemoteEndpointImplBase
      Parameters:
      opCode - The OPCODE for the message to be written
      timeoutExpiry - The time when the attempt to acquire the semaphore should expire
      Returns:
      true if the semaphore is obtained, otherwise false.
      Throws:
      InterruptedException - If the wait for the semaphore is interrupted

    • doWrite

      protected void doWrite(SendHandler handler, long blockingWriteTimeoutExpiry, ByteBuffer... buffers)
      Description copied from class: WsRemoteEndpointImplBase
      Writes data to the underlying connection.
      Specified by:
      doWrite in class WsRemoteEndpointImplBase
      Parameters:
      handler - the send handler
      blockingWriteTimeoutExpiry - the timeout expiry time
      buffers - the data buffers to write

    • updateStats

      protected void updateStats(long payloadLength)
      Description copied from class: WsRemoteEndpointImplBase
      Hook for updating server side statistics. Called on every frame written (including when batching is enabled and the frames are buffered locally until the buffer is full or is flushed).
      Overrides:
      updateStats in class WsRemoteEndpointImplBase
      Parameters:
      payloadLength - Size of message payload

    • onWritePossible

      public void onWritePossible(boolean useDispatch)
      Called when the underlying socket is ready for writing.
      Parameters:
      useDispatch - whether to use a dispatch for callback

    • doClose

      protected void doClose()
      Description copied from class: WsRemoteEndpointImplBase
      Performs the actual close operation on the underlying connection.
      Specified by:
      doClose in class WsRemoteEndpointImplBase

    • getTimeoutExpiry

      protected long getTimeoutExpiry()
      Returns the timeout expiry time in milliseconds.
      Returns:
      the timeout expiry time

    • onTimeout

      protected void onTimeout(boolean useDispatch)
      Handles a write timeout event.
      Parameters:
      useDispatch - whether to use a dispatch for callback

    • setTransformation

      protected void setTransformation(Transformation transformation)
      Description copied from class: WsRemoteEndpointImplBase
      Sets the transformation for this endpoint.
      Overrides:
      setTransformation in class WsRemoteEndpointImplBase
      Parameters:
      transformation - the transformation to use

    • getLock

      protected ReentrantLock getLock()
      Description copied from class: WsRemoteEndpointImplBase
      Returns the lock used for thread-safe operations.
      Specified by:
      getLock in class WsRemoteEndpointImplBase
      Returns:
      the reentrant lock