We have two applications running on same machine, both of them are listening on the loopback interface on two different ports. Client Application is sending data to server, but receiving Application (server) is receiving the data after 20 seconds.

CPU , RAM consumption looks normal. Currently we are suspecting Socket buffer size maybe full which results in Queuing of packets.

We captured on the loopback (lo) interface using tcpdump, but when the capture is opened using Wireshark it only shows the packets sent from the client side.

  • Is there anyway to filter the packet on the server side, when the server receives the packet in wireshark/tcpdump?
  • Also any other suggestion is welcome on how to debug further
  • Unfortunately, questions about host/server/VM configurations are off-topic here. For questions about internal to the host networks, you could try to ask on Server Fault. – Ron Maupin Jul 7 '18 at 20:22

I think you can see the traffic that is coming to the loopback but when the server send data it use directly the physical interface.

Anyway, tcpdump put the interface that you monitor in promiscous mode. Try to monitor directly the physical interface of the server that is used to forward your data and you will see everything (incoming and outcoming traffic).

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