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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

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Countermeasures versus incoming DNS reflection attack

i am currently experiencing a DNS reflection attack towards my server. I am getting a massive amount of answers via UDP from Port 53 that my server has never asked for: 02:53:57.626156 IP (tos 0x0, ttl 50, id 0, offset 0, flags [DF], proto UDP…
Marcel
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UDP packets to IP addresses other than specific ones not arriving and not shown in Wireshark

I'm writing a service using UDP, but I can't manage to reply to the client. When sending to the client via the DHCP-assigned IP (192.168.1.143) Wireshark shows no sent packets. The server receives and Wireshark shows any packet sent by the client…
Max
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iptables rules for botnet (UDP flood) protection

I'm currently experiencing a massive UDP attack on my server. I host a couple of gameservers, mainly Tf2, CS:GO, CS 1.6 and CS:Source, and my 1.6 server is being flooded. I tried different rules in iptables, but none of them seemed to work. I'm on…
Petar Simeonov
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Can NAT port change dynamically in an active session?

I am facing an issue, having client server application where client application is sending UDP data frequently to server and server redirecting back to the client. But in a few cases I am not getting packets at all on the client side. I checked on…
bharat
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Too much traffic on UDP suspecting bind miss-configuration

A server generates over 600GB of monthly traffic on UDP port (while http is under 1GB), so I ran tcpdump command and I see many (over 10/second or so) fast dns related commands/traffic that looks like this: 12:34:29.829750 IP avo.net.domain >…
adrianTNT
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Sonicwall IPS blocking Simple Help direct connection

We host a remote access tool called Simple Help. It allows us to access our clients computers and assist them with problems. I can log into it from my remote workstation, and connect to a clients workstation via our server. Then upon a successfully…
skinneejoe
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SNMP (UDP) Proxy

I'm Working in a mid-sized telco, and I'm in charge of network monitoring solutions. We have a custom monitoring system, that is using mostly SNMP to communicate with devices. The problem is that every once in a while, we need to add additional…
Jacket
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Confused! php-cgi opened (and didn't close) a UDP "connection" ...but isn't UDP connectionless?

This question is more for my own education than to solve any problem. I am running a VPS at linode w/ lighttpd and PHP 5.3.13 via fast-cgi. When I list internet connections, I get this strange creature: # lsof -i COMMAND PID USER FD TYPE…
CNYLiberty
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How to block specific UDP packet outgoing from machine using iptables

I want to block specific UDP packet OUTGOING from my machine using iptables. Packet has a string in "hex in RAW"(?) i want to check packet by it. Like: If UDP packet hex RAW match "test_text" - block it. //EDIT: i have something like this iptables…
wlodzimierz
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Very strange localhost connections on linux workstation. Need help identifiying the source

The following is the output of netstat on a Ubuntu machine. Can someone help decrypt the output? I am especially curious what the ::1:43213 connection is. Also, why are there so many connections from localhost to localhost on both v4 and v6…
Max Brown
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TCP what's the purpose of the third step of 3-way-handshake

Possible Duplicate: Why is it 3-way-handshake and not more? Example: If a client wants to talk to a server, it just tells the server that it wants to establish a connection, then the server confirms. People say that the third step's there so as…
IcySnow
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How to sniff udp between two windows applications on the same machine

How do I monitor the duplex udp traffic between two apps on my windows machine.
user111322
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Is there any way to set PPTP on UDP Protocol?

In our network,many web site has been filtered ,so we should use VPN or Socks ,They reduce any tcp connection speed by dropping random packet (Than post and get on http),So ssh,pptp and ... are so slow. Now I wanna to connect to my pptp server by…
Moein Hosseini
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Listing TCP/UDP process from an organically grown application

I've been asked to compile a list of TCP/UDP and ports they use for the collection of application that comprise our product for a client who wants the information for their firewall. So I fired up TCPView some of the processes are so short lived…
graham.reeds
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NAT UDP Hole punching beginner's basic Qn

Is there any simple example of UDP-NAT hole punching, capable of hole punching for 2 peers communication via internet? I am trying to do UDP hole punching so that it would be possible to NAT traversal. After going through the text available on the…
abhinav
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