checking if server closed the connection?

[baselzind]

I'm trying to reach a NVR (192.168.30.127) which is pingable through a pc (192.168.2.135) however when i open the page in the browser it gives me 

This page isn’t working

192.168.30.127 didn’t send any data.

ERR_EMPTY_RESPONSE

I tried to check the traffic using wireshark and I'm seeing the server sending me (fin,ack). does this means the NVR is closing the connection as in the attached wireshark screenshot and the problem isn't related to the network and switches?

[Georg Pauwen]

Hello,

what device (NVR ?) are you trying to access ? ERR_EMPTY_RESPONSE typically means no data is being sent/transmitted. What path is the traffic taking from source to destination, which intermediate devices are involved ?

The error could also be caused by the browser itself, check the link below:

https://ncu.libanswers.com/faq/221768

[baselzind]

well im trying to clear the network side as i can already ping the nvr which is a network video recording device. the connection is like this nvr>switch>switch>core switch. doesn't the Wireshark indicate that the server is closing the connection?

[Georg Pauwen]

Hello,

connect the end device directly to the NVR (or the switch that connects to the NVR), check if the problem persists, if not, connect the end device to the next downstream switch, that way, you can isolate the 'problem' device. Are the layer 2 or layer 3 switches ? If possible, post the full running configs of all switches (and put a description on the up/downlink ports so we know what is connected to what)...

[baselzind]

will do that first step , but the thing is ping is working fine and I'm getting response from the server. Isn't this enough to clear the network side as it is only edge switches and core switch without a firewall in between

[Georg Pauwen]

Hello,

ICMP (ping) is a good indicator for basic connectivity. however, something is obviously not working with http(s) traffic. Is the core a layer 3 switch ? Web traffic problems are often related to MTU settings...so if there is a layer 3 interface in the path towards the NVR, try and set the MTU to something like 1400 (and tcp adjust-mss to 1360). Which browser are you using, and what brand/type/model is the NVR ?

[baselzind]

there is a layer 3 in the core switch with the vlan interfaces but trying from the same subnet yield the same result

[marce1000]

                             Ref : https://shapeshed.com/unix-wget/

 - Try to fetch the particular url (or address in this case with) : wget  , check if you can find additional info's

 M.

[MHM Cisco World]

try telnet using the port, 
and share output here

[baselzind]

did it from the core 

telnet 192.168.30.127 80
Trying 192.168.30.127, 80 ... Open

[Connection to 192.168.30.127 closed by foreign host]

[MHM Cisco World]

that Good meaning the Port is open, 
now the WS is mismatch between the Server and client, 
go to client PC disable the Window Scale parameter
https://docs.microsoft.com/en-us/troubleshoot/windows-server/networking/description-tcp-features

[baselzind]

what is WS and how did you know it is mismatched between client and server?

[MHM Cisco World]

during TCP exchange of Data there is Window large or small when one side need to, this window like message tell other peer that I have only this free buffer to receive data,

this window has size called window scale.

in your wireshark TCP handshake I see 
SYN with WS=256
SYN & ACK with WS=64
so both side not agree on the WS other side use.

so since the SYN always from the client then disable it
or in Server side enable it.