Im using tcpdump to generate some captures between a client, proxy and an origin server.
I was wondering if its possible to either within wireshark or thru some param to indicate in each packet what TCP status the device is at e.g. ip 10.20.30.34 -- CLOSE_WAIT etc..
This is not possible within Wireshark (and AFAIK not within tcpdump either).
Related
My question is that how the destination port address in UDP is chosen/given?
I mean what matters to set a destination port in a UDP packet?
Because when we send a packet, just the destination address(ip) is important and we want to send data to our destination.
It has nothing to do with the port!
Do we assign a random port?
Typically, whatever documentation tells you what to put in the UDP datagram you're sending should also tell you what port to send it to.
For example, if you're trying to talk to an NTP server, RFC5905 tells you what to put in the UDP datagrams you send. It also tells you, on page 16, to send it to port 123.
If you're writing a DNS resolver, RFC1035 is one place you might look for the information needed to know what to put in your UDP datagrams. It also tells you, in section 4.2, to send the datagrams to port 53.
So however you're figuring out what to put in the UDP datagrams you're going to send, that's typically what tells you either what port to send them to or, in some cases, how to determine what port to send them to.
For example, a media streaming protocol might start with the information about the stream being delivered by a web server. In that case, the information delivered by the web server to the client might include the destination port to send datagrams to.
Generally, there's either a well-known port that at least one side listens for datagrams on or there's some external method using a different protocol that tells whichever end sends the first datagram what port to send it to. The other end then just replies, sending its response datagrams to whatever port that first datagram was sent from.
Generally, the sending port is chose randomly for the ephemeral ports available.
The destination port is the port to which the destination application is listening. To facilitate this, IANA maintains the Service Name and Transport Protocol Port Number Registry for standard applications and protocols.
If you create your own application or protocol, there is a range for you to use, but you should always check the registry to make sure you will not step on some other application or protocol.
When you design your listening application or protocol, you choose a port on which it listens, and the sending application will need to send to that port.
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 found netcat is very useful for listening TCP connection by using -l port-number, but I'm wondering if there is a more powerful tool available to analysis all incoming protocol, like RADIUS client request, so I can check out what the request are made of and if server get the request
netstat maybe the way to go with the -c flag, but it doesn't show even tcp connection with custom port number
any idea?
Wireshark offers a command line tool as well as a GUI (http://www.wireshark.org/)
Why don't you use netstat and grep the output to filter only the ports that you need?
The output is similar to this:
Proto Recv-Q Send-Q Local Address Foreign Address (state)
tcp4 0 0 192.168.1.7.63364 64.34.119.101.80 ESTABLISHED
tcp4 0 0 192.168.1.7.63357 64.34.119.13.80 ESTABLISHED
and it is very simple to grep results by protocol, port, address and state.
Bro is a (command-line) tool that extracts a wide range of information from network traffic. It is port agnostic, e.g., can detect HTTP on non-standard ports and features a application parsers for a variety of protocols. The connection log provides a lot of useful information at flow granularity, including:
Timestamp
Connection 5-tuple (source host, source port, destination host, destination port, transport protocol)
Application-layer protocol
Duration
Transport-layer bytes sent (source and destination)
Connection status
Number of packets (source and destination)
See this answer for example output.
I am trying to find out the type of the tunnel used for a vpn.. I am trying to determing if the tunnel is tcp or udp.. how do I do that? When I observe the tunnel traffic I am not able to observe anything! In the sense that packets are sent as such..
You need to observe the traffic on the physical network connection, not the traffic in the tunnel itself:
Setup a network packet capture program, such as Wireshark, to capture the traffic on the "real" network interface e.g. your cabled Ethernet connection. On Linux it would be something along the lines of eth0.
(Optional) Shutdown as many processes that use the network as possible.
Cause as much traffic through the VPN tunnel as possible - e.g. download a large file.
Watch in your capture program for any change - the tunnel traffic should now stand out due to sheer volume.
Keep in mind that if you are using an IPSec tunnel, the packets will be ESP, which is neither TCP nor UDP.
When sending data using UDP, a destination port is needed to be specified.
If sending by TCP, a source port should also be specified.
Are there different ports for input and output? E.g., if I specify port 1234, can I use it for both input and output or should I use different ports for output and input?
EDIT:
To clarify my question:
- I send data from port X.
- Someone sends data to me to port X.
Are those two different ports or is the same one used?
When sending data using UDP, a
destination port is needed to be
specified.
Correct.
If sending by TCP, a source port
should also be specified.
Incorrect. The system will allocate one for you automatically if not specified. This is the normal usage.
Are there different ports for input and output?
No. The local port you are bound to is used for both.
And all this applies to both UDP and TCP.
The source port is a port that exists only on the computer that is initiating the connection, whereas the destination port exists only on the computer that is receiving it (though both are visible to both endpoints). Both TCP and UDP have both source and destination ports. Usually the source port is selected automatically by the socket library from the unused ports on the computer. There are very few good reasons for selecting a specific source port, and it will often be changed by the Internet gateway (router) as a part of the Network Address Translation (NAT) process.
Edit: To clarify, both the source and destination ports are used for both input and output. Which port is on your computer depends on which end of the TCP connection you are on. If you are on the receiving end, then the destination port is on your computer. When you are looking at the connection from your perspective, it will be the source port, and will be used for both input and output. The same principle applies to UDP as well, except that there are no "connections" per se, merely an exchange of raw data between ports.
TCP needs both a source and a destination port because it forms a connection between the two clients, whereas UDP is connectionless; You simply send data to a destination port and it either arrives or not.
So with TCP, you open a "channel" between two computers. You send data through it and possibly receive some back.
With UDP, if you want to receive data, then yes you need a "separate" port that listens for incoming data.