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.
Related
In DHCP protocol we have 4 packets named DORA.
first of all client send a broadcast Discovery packet for detecting DHCP server.
Then server send a Offer packet contain ip, subnet and many options and waiting for client.
If client find Offer packet suitable, send a broadcast Request and get ACK or NAK.
But why ?
Why we can't ignore Request packet and replace this way to sending 3 packets.
Discovery, Offer and ACK.
client -> Discovery
server -> Offer
client -> ACK
Why this way is not secure or suitable ?
When the client broadcasts the Discover packet, it may get Offer packets from multiple DHCP servers. The purpose of the Request packet is to say to one of the servers, "I want to use the IP address that you offered to me". If that wasn't sent:
the server whose offered IP the client is going to use wouldn't know not to offer that IP to a different client, and
the other servers wouldn't know that they can offer their IPs to other clients.
Then the final Acknowledge packet tells the client that the server has gotten the Request, and that the client now has the "lease" on the IP address.
This is intended to ensure that:
IP addresses are not wasted because a server thinks the client is using the Offered IP, when the client is actually using a different server's Offered IP.
The same IP is not accidentally leased to two clients at the same ... which causes chaos.
In the variation that you proposed, suppose that the ACK packet from the client to the server is lost. Now the server won't realize that the client is going to use the Offered IP address. A few minutes later, it could then Offer the same IP address to a different client and ... chaos ensues.
Please don't imagine that the people who design internet protocols are dullards. They have thought these things through carefully before they write the RFCs. And many other (equally smart) people have gone over the pre-approved RFCs carefully looking for problems. So ... if there is something about a standard protocol that you think is wrong ... it is probably you, and not the protocol designer who is mistaken.
I have a question about packetloss in streaming (UDP protocoll) and I have packetloss with every Cloud-Gaming streaming provider and the only workaround is a VPN with TCP as protocoll.
The problem is that here in Germany the peering is totally bad so UDP packets on the way have problems to be transmitted properly.
VPN with TCP as a protocol creates help here by packing the UDP packets in a TCP frame (I think) and then routing them.
As soon as I switch the VPN off or back to UDP I have packetloss again, TCP is the only way I can get rid of the streaming problem, unfortunately one can't select TCP as protocoll in the settings of the cloud providers, so I have to rely on VPN with TCP.
Sadly the ping and the response time increases a lot, because the route is extended and therefore overhead is created.
Are there other ways to force streaming over TCP? Maybe via Windows GPO/Registry or router settings?
I don't want to rely on VPNs, as they cost money and improve the experience in general, but don't solve the problem overall.
I have no filters applied, but am not seeing any traffic other than what appear to be conversations at the Link Layer between my computer's NIC and the router. It is connected via Ethernet, and I believe at one time I could see HTTP, TCP, UDP, etc.
Any suggestions would be appreciated. I've tried visiting Websites and received nothing clearly from those sites.
If a client inside firewall connects to a public server through TCP, once the connection is formed, the firewall allows two-way communication. This is what we normally see in our daily usage. My question is: is this also true for UDP?
Since UDP does not have connect, I will modify the question a little bit...
Suppose the client inside firewall sends a UDP packet to a public server, can the server respond back through firewall using the source address and port of incoming packet?
Yes this is called NAT traversal (or UDP punch through) and works in a similar way to TCP - the stateful NAT device is aware you recently sent a UDP packet from a certain end point internally to a certain end point outside and for a period will accept UDP packets from the same outside endpoint and forward them to the same internal end point.
I always prefer the IETF docs than the plethora of conflicting information out there (including on this site):
https://www.rfc-editor.org/rfc/rfc5128
UPDATE: There are other techniques to "UDP hole punching" such as UPnP's Internet Gateway Protocol and PCP. Each has their advantages and disadvantages and I am afraid there is no one solution works on all NATs!
What is TCP response packets?
How to meet this requirement in access-list on a router?
You probably want to look up stateful firewalling for whatever router you're using.
TCP response packets are basically any related TCP packets that come back after an initial SYN has been sent. Typically this would be either a packet with SYN+ACK set, or one with RST if the connection was refused.
Stateful firewalls keep track of not just the source and destination of individual packets, but what connection the packets belong to. By doing this they are able to distinguish between expected, legitimate replies to SYN packets (and others) and random or malicious unrequested "replies".