In 8.3 the default TCP keep alive settings introduced in https://github.com/elastic/elasticsearch/pull/59278 are not applied by default, therefore it uses the OS default values. See:

8.3.0:
```
cat connections-8.3.0.txt  | grep -e '930[01]' | head
ESTAB  0       0         [::ffff:127.0.0.1]:46818     [::ffff:127.0.0.1]:9301    timer:(keepalive,119min,0) uid:1038 ino:6837419 sk:a2 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37928     [::ffff:127.0.0.1]:9300    timer:(keepalive,119min,0) uid:1038 ino:6834869 sk:a3 <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46808   timer:(keepalive,119min,0) uid:1038 ino:6830957 sk:a4 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37942     [::ffff:127.0.0.1]:9300    timer:(keepalive,119min,0) uid:1038 ino:6834871 sk:a5 <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46828   timer:(keepalive,119min,0) uid:1038 ino:6834882 sk:a6 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37926     [::ffff:127.0.0.1]:9300    timer:(keepalive,119min,0) uid:1038 ino:6834868 sk:a7 <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46826   timer:(keepalive,119min,0) uid:1038 ino:6834881 sk:a8 <->
ESTAB  0       0         [::ffff:127.0.0.1]:46824     [::ffff:127.0.0.1]:9301    timer:(keepalive,119min,0) uid:1038 ino:6837425 sk:a9 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37944     [::ffff:127.0.0.1]:9300    timer:(keepalive,119min,0) uid:1038 ino:6834879 sk:aa <->
ESTAB  0       0         [::ffff:127.0.0.1]:46828     [::ffff:127.0.0.1]:9301    timer:(keepalive,119min,0) uid:1038 ino:6837430 sk:ab <->
```

8.2.2:
```
cat connections-8.2.2.txt  | grep -e '930[01]' | head
ESTAB  0       0         [::ffff:127.0.0.1]:46752     [::ffff:127.0.0.1]:9301    timer:(keepalive,4min52sec,0) uid:1038 ino:6833637 sk:6e <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46746   timer:(keepalive,4min52sec,0) uid:1038 ino:6831684 sk:6f <->
ESTAB  0       0         [::ffff:127.0.0.1]:46732     [::ffff:127.0.0.1]:9301    timer:(keepalive,4min52sec,0) uid:1038 ino:6833629 sk:70 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37876     [::ffff:127.0.0.1]:9300    timer:(keepalive,4min52sec,0) uid:1038 ino:6833618 sk:71 <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46730   timer:(keepalive,4min52sec,0) uid:1038 ino:6831676 sk:72 <->
ESTAB  0       0         [::ffff:127.0.0.1]:46748     [::ffff:127.0.0.1]:9301    timer:(keepalive,4min52sec,0) uid:1038 ino:6833640 sk:73 <->
ESTAB  0       0         [::ffff:127.0.0.1]:46736     [::ffff:127.0.0.1]:9301    timer:(keepalive,4min52sec,0) uid:1038 ino:6833631 sk:74 <->
ESTAB  0       0         [::ffff:127.0.0.1]:9301      [::ffff:127.0.0.1]:46732   timer:(keepalive,4min52sec,0) uid:1038 ino:6831677 sk:75 <->
ESTAB  0       0         [::ffff:127.0.0.1]:37860     [::ffff:127.0.0.1]:9300    timer:(keepalive,4min52sec,0) uid:1038 ino:6833611 sk:76 <->
ESTAB  0       0         [::ffff:127.0.0.1]:46734     [::ffff:127.0.0.1]:9301    timer:(keepalive,4min52sec,0) uid:1038 ino:6833630 sk:77 <->
```

It's possible that after moving `NetUtil` to the netty module https://github.com/elastic/elasticsearch/pull/85953 some of the internal details used are not available anymore.
modules/transport-netty4/src/main/java/org/elasticsearch/http/netty4/Netty4HttpServerTransport.java
}
                    }
                    if (SETTING_HTTP_TCP_KEEP_COUNT.get(settings) >= 0) {
                        final SocketOption<Integer> keepCountOption = NetUtils.getTcpKeepCountSocketOptionOrNull();
                        if (keepCountOption != null) {
                            serverBootstrap.childOption(NioChannelOption.of(keepCountOption), SETTING_HTTP_TCP_KEEP_COUNT.get(settings));
                        }
                    }
                }
            }
            final ByteSizeValue tcpSendBufferSize = SETTING_HTTP_TCP_SEND_BUFFER_SIZE.get(settings);
            if (tcpSendBufferSize.getBytes() > 0) {
                serverBootstrap.childOption(ChannelOption.SO_SNDBUF, Math.toIntExact(tcpSendBufferSize.getBytes()));
            }
            final ByteSizeValue tcpReceiveBufferSize = SETTING_HTTP_TCP_RECEIVE_BUFFER_SIZE.get(settings);
            if (tcpReceiveBufferSize.getBytes() > 0) {
                serverBootstrap.childOption(ChannelOption.SO_RCVBUF, Math.toIntExact(tcpReceiveBufferSize.getBytes()));
            }
            serverBootstrap.option(ChannelOption.RCVBUF_ALLOCATOR, recvByteBufAllocator);
            serverBootstrap.childOption(ChannelOption.RCVBUF_ALLOCATOR, recvByteBufAllocator);
            final boolean reuseAddress = SETTING_HTTP_TCP_REUSE_ADDRESS.get(settings);
            serverBootstrap.option(ChannelOption.SO_REUSEADDR, reuseAddress);
            serverBootstrap.childOption(ChannelOption.SO_REUSEADDR, reuseAddress);
            bindServer();
            success = true;
        } finally {
            if (success == false) {
                doStop(); 
            }
        }