From 7bc8fa10c4687f2197828e2fa1b0726020583dcb Mon Sep 17 00:00:00 2001
From: marci4 <marci4@live.de>
Date: Thu, 9 Nov 2017 18:55:46 +0100
Subject: [PATCH] Check for sending a close frame

#579
---
 pom.xml                                             |  3 +++
 src/main/java/org/java_websocket/WebSocketImpl.java | 12 +++++++-----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/pom.xml b/pom.xml
index af404f41..f851cb5e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -7,6 +7,9 @@
   <name>Java-WebSocket</name>
   <description>A barebones WebSocket client and server implementation written 100% in Java</description>
   <url>https://github.com/TooTallNate/Java-WebSocket</url>
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
   <licenses>
     <license>
       <name>MIT License</name>
diff --git a/src/main/java/org/java_websocket/WebSocketImpl.java b/src/main/java/org/java_websocket/WebSocketImpl.java
index 97d387d0..1ea6dfdb 100644
--- a/src/main/java/org/java_websocket/WebSocketImpl.java
+++ b/src/main/java/org/java_websocket/WebSocketImpl.java
@@ -424,11 +424,13 @@ public void close( int code, String message, boolean remote ) {
 								wsl.onWebsocketError( this, e );
 							}
 						}
-						CloseFrame closeFrame = new CloseFrame();
-						closeFrame.setReason( message );
-						closeFrame.setCode( code );
-						closeFrame.isValid();
-						sendFrame( closeFrame );
+						if (isOpen()) {
+							CloseFrame closeFrame = new CloseFrame();
+							closeFrame.setReason( message );
+							closeFrame.setCode( code );
+							closeFrame.isValid();
+							sendFrame( closeFrame );
+						}
 					} catch ( InvalidDataException e ) {
 						wsl.onWebsocketError( this, e );
 						flushAndClose( CloseFrame.ABNORMAL_CLOSE, "generated frame is invalid", false );