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GeezerVison is showing github.com — Allow configuration of TCP keepalive for NIO TCP connections · Issue #420 · dnsjava/dnsjava

Allow configuration of TCP keepalive for NIO TCP connections #420

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Allow configuration of TCP keepalive for NIO TCP connections#420
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@MarioGoupil
MarioGoupil
opened on Oct 3, 2026
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When dnsjava receives a truncated UDP response, it retries the query over TCP using NioTcpClient. That created TCP connection may remain open for reuse, but currently there is no way to configure TCP keepalive. A firewall or other network device may silently drop an idle connection, causing later queries that reuse it to fail.
Enabling SO_KEEPALIVE on NIO TCP connections and allowing callers to configure the keepalive timing and probe count would prevent that. Suggested system property names and defaults:

Property Default Socket option
dnsjava.tcp.keepalive true SO_KEEPALIVE
dnsjava.tcp.keepidle 900 seconds TCP_KEEPIDLE
dnsjava.tcp.keepinterval 75 seconds TCP_KEEPINTERVAL
dnsjava.tcp.keepcount 9 probes TCP_KEEPCOUNT

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  1. ibauersachs
    added
    enhancement
    volunteer wanted
    on Oct 20, 2026

  2. ibauersachs commented on Oct 20, 2026

    @ibauersachs
    ibauersachs
    on Oct 20, 2026
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    Thanks for the suggestion. While these settings might help, they go into territory of RFC7828 and should probably be implemented together. Would you mind contributing this with a PR?

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