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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How are UDP datagrams that don't have me as a recipient reaching my server?

I have a bunch of UDP datagrams reaching my server that look like so: The question is, my IP is not 208.69.57.21, (it was 208.69.57.101) so how are those datagrams even being received/logged by my tcpdump? Also, what kind of attack is this formally…
bobobobo
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Connect to internet via udp protocol

Is it possible if firewall blocking all http trafic but udp protocol is open connect to internet? because skype use udp protocol to connect and users can use skype. But is technicaly possible to cheat it and use proxy to connect to web via udp…
Reno
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How to optimize TCP / IP stack in Linux?

Currently I noticed there are about 15K open connections to localhost. It is mainly connecting to Memcached. I am clueless where I should start to optimize TCP/IP stack. Memcached support UDP, but the PHP library doesn't support it. The server has…
mary
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Why would a UDP socket perform OK on wifi, but not on a cell network?

Noobish question - I have a perl script running on a linux server which opens UDP port 7015. netstat -ulnp shows: udp 0 0 0.0.0.0:7015 0.0.0.0:* 16365/perl nmap -sU -p 7015 'hostname' on a…
softex
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What settings should I modify to tune a Linux server for very small yet very high packet rate UDP receive loads?

I am tuning a server that needs to handle small (average of about 50 bytes) UDP packets. The average packet rate is approximately 100,000 packets/second. The data is very burst and can sometimes burst to 5x the mean packet rate. What settings should…
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tc: packets filter

I need to drop UDP packets with specific UDP port number) on network interface (say eth0). On my setup the interface eth0 is part of the bridge. is it possible to do it using tc command? if yes, how?
Dima
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shell record UDP stream from a specific address

I'm trying to record an incoming UDP stream (stream the sense that it's a stream of consecutive datagrams). I tried netcat but unfortunately multiple sources send data on the same port address and nc doesn't let you specify the source or the target…
Karoly Horvath
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Which UDP ports are required to resolve external hosts?

Today I asked my hoster to block all UDP ports except port 53. Due to daily UDP attacks, this was currently the only option to stop flooding my lines. Now since the block is in place, I cannot wget anything anymore. [root@s1 wupload]# wget…
Mr.Boon
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Block All UDP traffic (to prevent ddos)

I have been receiving countless ddos attacks the last couple of weeks. Just now I caught one while I was running iptraf. Normally 99.9% of the packets used on my server are TCP packages, and not UDP. A few are used I see, but normally hardly…
Mr.Boon
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UDP Protocol - ICMP Error Generation

I know that UDP has no real error control facilties outside of silent discard of packets failing checksums. Am I correct in thinking that a UDP packet with a TTL=1 reaching a router will generate an ICMP Time Exceeded message, and a UDP packet…
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Hosting a UDP Server

How do I host a UDP server for free or cheap? I can't afford to actually buy or rent a physical server. I have a prototype server application written in C#, and I can probably rewrite it in any platform or language. What's the easiest way to do…
user434565
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how to enable port 7777

I am initiating file transfer using tcp on openfire server. But I am not able to open the port number 7777, from which I need to send files. I changed the security setting in the admin console panel of the aws. But still when I tried to send the…
Jeevan Dongre
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UDP pseudoheader

Is it true that in the UDP header 2 bytes store a checksum for verification purposes by the destination host, and that this checksum is generated from a pseudoheader? If this is true, then why does a pseudoheader even have to be created? Why not…
Wintermute
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Network UDP logger with replay

I need network logger utility with ability to replay the data it collected, for example, I will record incoming data on UDP port 1234 for 10 minutes, record it to file, then replay that data (with same timing) to some other address:port. It has to…
Daniel Mošmondor
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Can a network interface be configured to have a default gateway for UDP packets?

It is quite possible that my question may not make a lot of sense. I apologize, but I am not a networking guy, and that's my excuse. To elaborate, WikiPedia defines "Default Gateway" as a node on a "TCP/IP" network. And the way it works is that if a…
Vaibhav
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