Added setAttachment and getAttachment to WebSocket interface

src/main/java/org/java_websocket/WebSocket.java

@@ -220,4 +220,21 @@ enum READYSTATE {
 	 * @return Returns the decoded path component of this URI.
 	 **/
 	String getResourceDescriptor();
+
+	/**
+	 * Setter for an attachment on the socket connection.
+	 * The attachment may be of any type.
+	 * 
+	 * @param attachment The object to be attached to the user
+	 * @since 1.3.7
+	 **/
+	<T> void setAttachment(T attachment);
+
+	/**
+	 * Getter for the connection attachment.
+	 * 
+	 * @return Returns the user attachment
+	 * @since 1.3.7
+	 **/
+	<T> T getAttachment();
 }

src/main/java/org/java_websocket/WebSocketImpl.java

@@ -145,6 +145,12 @@ public class WebSocketImpl implements WebSocket {
 	 */
 	private PingFrame pingFrame;
 
+	/**
+	 * Attribute to store connection attachment
+	 * @since 1.3.7
+	 */
+	private Object attachment;
+
 	/**
 	 * Creates a websocket with server role
 	 *
@@ -799,4 +805,15 @@ public WebSocketListener getWebSocketListener() {
 		return wsl;
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public <T> T getAttachment() {
+		return (T) attachment;
+	}
+
+	@Override
+	public <T> void setAttachment(T attachment) {
+		this.attachment = attachment;
+	}
+
 }