Unexpected exception in multicast receiver – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.

To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.

This guide will help you check for common problems that cause the log ” Unexpected exception in multicast receiver ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: discovery, discovery-multicast and Plugin.

Log Context

Log “unexpected exception in multicast receiver” classname is MulticastChannel.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                         if (datagramPacketReceive.getData().length > 0) {
                            listener.onMessage(new BytesArray(datagramPacketReceive.getData()); datagramPacketReceive.getSocketAddress());
                    } catch (Throwable e) {
                        if (running) {
                            logger.warn("unexpected exception in multicast receiver"; e);


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