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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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rx_missed_errors with ring size set to maximum - udp bursts

Application A sends traffic to B via TCP. B using multicast (UDP) sends traffic further to C. Applications on D get this data via TCP. A -> (TCP) -> B -> (UDP) -> C -> (TCP) -> D A - Windows Server B - Linux VM on ESX host C - Linux VM on another…
LinuxGuy123
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FreeBSD: redirect some UDP traffic from one port to another

I have some specialized DNS servers running on FreeBSD 11. A few people keep hammering on them and I would like to give them different answers. So I'd like to divert UDP traffic from those hosts from port 53 to port 5300 where a different server is…
John Levine
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Why is my computer making unreachable ICMP requests to the gateway?

After playing around with the ICMP filter on wireshark, I noticed that my machine is making ICMP requests to the router regularly, which consistently fails: I noticed that the subsequent ICMP requests which fail are using UDP on port 53. Could…
Daniel Minnaar
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Conntrack is blocking UDP NAT

I'm working on an application that should relay udp packets from one host to another according to some rules. It is basically NAT. I negotiate UDP ports with both hosts and after that I need to receive from host A and send to host B with the…
Vargas
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KVM virtualized CentOS can send/recieve TCP but not UDP

I've installed CentOS 5 inside KVN on FC12. I've setup a bridged network that works fine. I can ping the virtualized host from any of my other computers and the other way as well. I can also access apache on the virtualized host from other computers…
Ron
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IPVS (keepalived) doesn't balance UDP connections

I have two load balancer with Debian 8 and three Graylog server with Debian 9. Every server in my network sends logs via rsyslog to a virtual server configured on the LB. The connection is UDP. The problem is that the packets are not balanced. (all…
mirobertod
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How does UDP sockets know which source address to respond to?

I have understood that UDP sockets are fully identified by destination IP and destination port. The IPs are in the IP datagram´s header yes, but when the datagram arrive at its destination, only the payload is sent to the upper-layer protocol. If…
Ramriez
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Is a DDoS possible if the port being attacked is closed?

Let's assume a hypothetical situation in which port 50000 of a machine was being bombarded with UDP packets. However, port 50000 on said machine isn't actually open (i.e. the machine is not listening on port 50000). Would such a bombardment of…
Ash
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netdata ipv4 UDP errors

I've recently installed netdata on an Amazon EC2 debian instance that I have. Netdata is pretty cool, nice charts/graphs, painlessly easy to install (compared to others.) A number of times each day I receive a message such as 1m ipv4 udp receive…
bo gusman
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Wireshark under Windows: Any way to capture packets before dropped by special filter drivers?

I've got some GigabitEthernet Vision cameras, which use Ethernet to communicate. The protocol is simple UDP, but for performance reasons (high packet throughput causing CPU load) the manufacturer uses a filter driver that prevents those packets from…
SDwarfs
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CentOS (with firewalld) - Forward udp (netbios) broadcast

I'm trying to implement a small lab infrastructure with VSphere with multiple LAN, 2 of the LANs are : Work : with employee laptops Trusted : With all my server (except web that is in a separate DMZ) Between those LANs I've a CentOS host with…
tomatediabolik
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OpenVPN TCP 443

I'm running an OpenVPN Server Version 2.4.4 on my Ubuntu 16.04.3. The VPN connections work absolutely fine with UDP 1194 but when I try to change to TCP 443 it just won't connect. Im using an apache2, which I turned off before testing with the…
obeN
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Set Windows Firewall to Stateless?

Is there a way to "dumb down" the Windows Firewall on Win2003 or Win2008 from stateful to "stateless", and have it only do basic port filtering on the public interface? If not, is there a simple, stateless software firewall I can replace Windows…
martona
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Nagios check_udp_ports returning critical: result to scheduled check, runs fine manually

We use a Nagios core 4.3.2 solution on Ubuntu 14.04 to do simple host check monitoring on remote client equipment. One type of device we use is not availible to ping, but as part of it's proprietary control system has the UDP port 5246 open…
HHMsig
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OpenVPN Server PacketLoss

I have an OpenVPN server with Debian 8 and OpenVPN 2.3.14 x86_64-pc-linux-gnu. Today I have realised packet loss. My server is on TCP port 443. Ping statistics for 144.76.41.103: Packets: Sent = 1135, Received = 1121, Lost = 14 (1%…
George
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