From fc30bf2f448ec7c87000cf2c1b4db43e36f041f4 Mon Sep 17 00:00:00 2001
From: Richard Hosking <richard@hovis.net>
Date: Tue, 30 Jul 2019 11:37:55 +0100
Subject: [PATCH] Fix ConcurrentModificationException when iterating through
 connections returned by getConnections()

---
 src/main/java/org/java_websocket/server/WebSocketServer.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/java_websocket/server/WebSocketServer.java b/src/main/java/org/java_websocket/server/WebSocketServer.java
index ceba5da6..07c7417c 100644
--- a/src/main/java/org/java_websocket/server/WebSocketServer.java
+++ b/src/main/java/org/java_websocket/server/WebSocketServer.java
@@ -279,7 +279,9 @@ public void stop() throws IOException , InterruptedException {
 	 * @since 1.3.8
 	 */
 	public Collection<WebSocket> getConnections() {
-		return Collections.unmodifiableCollection( new ArrayList<WebSocket>(connections) );
+		synchronized (connections) {
+			return Collections.unmodifiableCollection( new ArrayList<WebSocket>(connections) );
+		}
 	}
 
 	public InetSocketAddress getAddress() {