I am new to wireshark and to networking in general, but I am monitoring the traffic of my application and I can filter on it so I can see when it is actively transfering data that it is supposed to with the server but wireshark shows this:
protocol = TCP
length = 54
info = 56705 > ms-wbt-server [ACK] Seq=1 Ack=61 Win=252 Len=0
being fired every second from my app to my app server. Why does my application keep sending these packets every second?
It is a c# .net app if that is of any assistance.
It's a TCP keepalive packet, containing no data but with the ACK flag set. Just tells the other end you are still there, and keeps the connection open.
There's a good overview here:
http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html
ms-wbt-server is port 3389, and is used for the Remote Desktop Protocol (RDP), do you have a remote desktop connection open to your server by any chance?
Related
The below screenshot shows the relevant packets I am analysing on my laptop. I am confused as to why source port number is increasing by 1. And also I am not sure what and why this large number of SYC/RSTs are coming from.
wireshark print screen
Port 9229 is the default node.js debugging port.
When you open DevTools in your browser, it automatically starts trying to connect to port 9229. If you are not running a node debug server then the debugger client fails to form a TCP connection.
The large number of [SYN] / [RST, ACK] packets are basically the debugging client trying to connect. For each new connection request, the browser requests from a new port increasing it by 1.
In a TCP connection, the [RST] flag is set to reset the connection. It indicates that the receiver should delete the connection without further interaction (source: TCP RFC). Here, the [RST] flag signifies that port 9229 is not accepting any TCP connections.
You can fix it by closing all the DevTools windows in your browser.
You can also try to run a simple HTTP server in node with the command node --inspect server.js and then launch the DevTool window to check that these [RST, ACK] packets are gone and the DevTools window has a made a successful TCP connection.
I have been analyzing packets sent out from my IP to a game server.
The connection to the server was getting reset for some reason and after packet capture, I could see that there are TCP RST packets sent at the time of the disconnection.
I have tried to use advance firewall to specifically only restrict the TCP RST packets to the game server to see if that will prevent this disconnection. However I am unable to specify the flag level details in the rules.
How can I accomplish this configuration?
Is there any third party firewall that can do this?
Thank you
I am using wireshark, and for an exercise we need to capture a UDP packet with wireshark by visiting any website, and then analyze the information within that packet.
I have tried numerous times and all websites appear to send packets with TCP protocol. I have looked at Wireshark documentation, as well as looked online and am stumped.
What am I doing wrong, and how can I get a UDP packet by visiting a website?
Thats the main question. A side question is: how do I filter the captured packets to only those packets referring to requests and responses from websites over the network? Currently there appear to be a bunch of low-level captured packets that I need to scroll through.
Thanks in advance!
Because websockets/HTTP is over TCP.
And in Wireshark,if you are intending to see packets corresponding to a particular client/server, click on the packet and do "Follow TCP/UDP stream"
You will never see a UDP packet in a WEB connection. Never never never. The Web's connection is in HTTP protocol and HTTP is encapsulated in TCP.
If you need see UDP packets en wireshark you can generate UDP sockets from your host. You can:
Make a connection with a TFTP server.
Renew your IP you will see the DHCP protocol.
You search, what protocols are encapsulated in UDP and use it.
Make a program with UDP sokects.
I have around 20 clients communicating together with a central server in the same LAN. The clients can make transaction simultaneously with the server. The server forward each transaction to external appliance in the network. Sometimes it works, sometimes my application shows a "time out" message in a client screen (randomly)
I mirrored all traffic and found TCP Retransmission after TCP Reset packets for the first TCP Sequence. I immediately thought about packet loss but all my cables/NIC are fine, and I do not see DUP ACK in the capture.
It seems that RST packets may have different significations.
What causes those TCP Reset?
Where should I focus my investigation: network or application design ?
I would appreciate any help. Thanks in advance.
Judging by the capture, I assume your central server is 137.56.64.31. What's happening is the clients are initiating a connection to the server with a SYN packet and the server responds with a RST. This is typical if the server has no application listening on that particular port e.g. the webserver application isn't running and a client tries to connect to port 80.
The clients are all connecting to different ports on the server, which is unusual for an central server, but not unheard of. The destination ports the clients are connecting to on the server are: 11007, 11012, 11014, 11108, and 11115. Is that normal for the application? If not, the clients should be connecting to whatever port the application server is listening on.
The reason for the retransmits is that instead of giving up on the connection upon receiving a RST from the server, the client tries to initiate the connection again so Wireshark considers it a retransmission.
I am confused that if ports serve to distinguish the applications , so as to tell to which particular application data packet belongs , then if i have two browsers both downloading file using FTP , how would packet be distinguished to which brower it is going, as FTP uses port 21 ?
FTP is not the best example as it's behaviour change depending on Active/Passive mode.
Consider HTTP instead, which is simplier.
Browser_A initiates a TCP connection to ServerIP:80
PC assigns a random port, example HostIP:55123
TCP Connextion between HostIP:55123 and ServerIP:80 is established
Server receives a request and responds to HostIP:55123
PC knows every TCP packet from ServerIP:80 to 55123 should be delivered to Browser_A
First of all port 21 is COMMAND port, so when downloading file for sure FTP clients will not be connected to port 21.
Secondly, a connection is established from a high port (> 1024) to the FTP data port, so your browsers will open (in PASSIVE mode) a connection from a high port.
Answering to your question, if you open 2 browsers and start downloading data from FTP server, every browser will connect from a different port.