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Questions tagged [udp]

UDP stands for User Datagram Protocol. With UDP applications can send messages (datagrams) to other hosts on a network without requiring prior communications to set up special transmission channels or data paths.

Because UDP doesn't rely on handshaking to guarantee that packets arrive and in order it can be seen as an unreliable protocol, but for real time systems where acting on the data immediately is the most important consideration not having to wait for delayed packets is a distinct advantage.

UDP is just one communications protocol on the web. Others include:

  • Transmission Control Protocol (TCP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

UDP on Wikipedia

364 questions
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UDP traffic through SSH tunnel

The title pretty much sums it up. I would like to send UDP traffic through a SSH tunnel. Specifically, I need to be able to send UDP packets through the tunnel and have the server be able to send them back to me on the other side. I know how to…
heavyd
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56
votes
2 answers

What does SSH use UDP for?

Wile doing research I noticed that SSH both uses TCP and UDP. I completely understand the use of TCP, but UDP seems a bit strange. Why would I use an "unreliable" transport protocol with minimal handshaking for secure shell access? The only use I…
alex
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42
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8 answers

Why is it bad to have open ports?

Here's something that has always baffled me. Why is it bad to have open ports on your computer? Assuming you don't have a virus on your computer or some other program listening to a port that may actually do something why does it matter if a port is…
aireq
  • 681
33
votes
5 answers

How to generate UDP packet

I want to generate UDP packet to test a program, something equivalent to using telnet to test TCP port (Can telnet generate UDP packet?) How can I do this?
Lydon Ch
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25
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3 answers

How to use UDP hole punching for a SSH tunnel / session

I want to deploy a Raspberry Pi in my weekend cottage. The Raspberry Pi is there to log the temperatures and send them to a remote server which has a fixed ip, saves the data and displays it on a simple website. However the situation may arise that…
Christian
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25
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2 answers

what is type of ICMP packets? TCP or UDP

The ping packet is a type of ICMP packet. Is there any relation between ICMP with TCP? In other words, can we guarantee their arrival in the network? I want to know if ICMP packets in the network are TCP, UDP, both or none of them?
Mohammad Reza Rezwani
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22
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3 answers

NAT and UDP replies

Sanity check please. If I send UDP packets from Machine A behind a NAT to Machine B's port N, where Machine B is outside the NAT (elsewhere on the Internet), can I reasonably expect that NAT to pass UDP packets received from Machine B on port N back…
tomfanning
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20
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Why is my UDP so slow?

I'm using Iperf on two VMs and when using TCP I find the performance is as follows: notroot@ubuntu:~$ iperf -s ------------------------------------------------------------ Server listening on TCP port 5001 TCP window size: 85.3 KByte…
44800erpp
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19
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3 answers

Netcat/socat behavior with piping and UDP?

I guess this is close to linux - Netcat stops listening for UDP traffic - Super User, but I thought I'd better ask anyways As far as versions of netcat I'm using Ubuntu 11.04 and the default netcat on it, which I'm guessing is the openbsd one: $…
sdaau
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19
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3 answers

Does it matter what UDP port a WOL signal is sent to?

i have seen many WOL instances use port 7 and many use port 9, does it matter? Isn't it just looking for a WOL packet at layer 2 or ethernet?
rjt
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18
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7 answers

Linux built-in or open source program to join multicast group?

I'm using tcpdump to capture multicast packets and had to code up a custom program to join multicast feeds so tcpdump will "see" the packets. Just wondering if netcat or any other applications can perform this function instead?
chriskirk
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15
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4 answers

Tunnel wireguard (or any UDP traffic) inside HTTPS

Wireguard is pretty hot these days, deservedly so. I'm also eager to replace OpenVPN by Wireguard. However, unlike OpenVPN, Wireguard only supports UDP. I like to use TCP port 443 because this port is likely not blocked by a firewall. OpenVPN…
Volker
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14
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3 answers

Is it possible to process millions of datagrams per second with Windows?

I am investigating if I can implement an HPC app on Windows that receives small UDP multicast datagrams (mostly 100-400 Bytes) at a high rate, using a dozen or up to maybe 200 multicast groups (i.e. using MSI-X and RSS I can scale to multiple…
Evgeniy Berezovsky
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4 answers

How to detect if network is dropping UDP packets?

I'm got a video streaming application that runs fine in my office but fails miserably at the customer location. The symptom is that every couple of seconds, I stop receiving UDP packets for 2 seconds, then the stream resumes as if nothing is…
Gili
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11
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Why is there no UDP port forwarding in SSH?

I know SSH can forward TCP ports, not UDP. I'm not seeking help to circumvent this restriction, this subject is covered here. I'd like to know what is the reason SSH never got UDP forwarding ability. So far the answers to the already linked question…
Kamil Maciorowski
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