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.

learn more… | top users | synonyms

0
votes
0answers
36 views

How can I log and maybe even block IPs that send lots of incoming UDP traffic?

we run a voice / teamspeak server which receives legitmate traffic on port 9987 from many ips. Sometimes we get DDoSed. So people use single Servers and send 1-3 Gbits of UDP Floods to that port. This ...
1
vote
1answer
34 views

UDP Proxy with cloned packets

Having UDP messages sent from dynamic public IP periodically to public IP X:20000. Need a proxy that listens in IP X:20000, then forwards duplicate/clone packets to X:20001 and a different machine ...
1
vote
2answers
39 views

NAGIOS host availability test for host that can't be PINGed, won't talk to me, but can be traceroute'd

Part of my network estate has a fairly important dependency on a host whose availability is difficult to check. I have a number of hosts behind it, and my NAGIOS VPS provider occasionally has routing ...
2
votes
2answers
3k views

Reduce firewall rules by half - one iptables rule for tcp and udp

I have a number of iptables rules on my firewall that look like this: iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT Is ...
0
votes
0answers
50 views

How to turn a UDP feed on and off?

I have a linux application that is sending a stream of UDP packets to a particular ip and port. I need a way of suppressing this packet stream so the packets never reach the network, with the ability ...
2
votes
2answers
74 views

tcpreplay throughput on eth0 well below (iperf confirmed) max

I'm trying to replay captured UDP multicast packets at a rate of a couple of hundreds of Mbps, but it maxes out at about 86 Mbps. (For some strange reason, at other times during the day it ...
0
votes
0answers
14 views

Bonding connection or other techniques to improve UDP delivery

I have several VOIP servers linked by heavily loaded connections, and the voice quality gets pretty spotty at times. I have setup QoS to ensure upstream bandwidth is allocated favorably for VOIP, ...
14
votes
5answers
18k views

Linux Kernel not passing through multicast UDP packets

Recently I've set up a new Ubuntu Server 10.04 and noticed my UDP server is no longer able to see any multicast data sent to the interface, even after joining the multicast group. I've got the exact ...
3
votes
1answer
331 views

mosh-like port forwarding

This is on linux, connecting to linux servers: I love mosh, but it doesn't support port forwarding, and likely won't for a while since it's been almost a year now and it hasn't happened yet. port ...
1
vote
1answer
33 views

Netcat UDP File Transfer Between Two Servers Times Out?

I'm testing file transfer speeds between two Red Hat servers that are connected to the same switch within the data center and I decided to use netcat to eliminate protocol overhead as much as ...
3
votes
2answers
1k views

Many clients on a wireless AP for UDP broadcast packets

I asked this question on StackOverflow and was directed over here, so I'd appreciate any advice. I'm deploying a smartphone application as part of a live music performance that depends on receiving ...
0
votes
1answer
183 views

lots of UDP_IN Blocked errors

Since I have reinstalled my OS, I'm getting lots of UDP_IN Blocked errors in my messages log. Can anyone kindly explain what the error say exactly and what I can do to get rid of this error. Aug 8 ...
0
votes
2answers
311 views

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 ...
32
votes
11answers
23k views

What is the difference between UDP and TCP?

My router has two protocols (and a "both" option) that I can select when setting up port forwarding: UDP and TCP. What is the difference between these two protocols and when would you select one over ...
0
votes
1answer
95 views

UDP packet loss cause

I have two machines connected to the same LAN and multicasting UDP streams at rate of about 30Mbps. Analyzers often show packet losses on one machine, but never on another. What could be the reasons ...
3
votes
2answers
561 views

Symmetric NAT and UDP Hole Punching

I've read this question, but the explanation of Symmetric NAT wasn't detailed enough. Please could someone help me to understand the following paragraphs? I read this about Symmetric NAT: Each ...
0
votes
2answers
49 views

UDP Packet drop? [closed]

Multicast packet got drop between the server, multicast work on udp which unreliable so drop packet is expected Question: is their a way or utility available to capture udp packet at os kernel ...
3
votes
1answer
240 views

Difference between /dev/udp and netcat

I have a syslog server listening on localhost:514 as UDP and would like to write messages to it on that port. (Using Ubuntu 14.04) If I run either of these commands this from bash it prints the date ...
2
votes
2answers
1k views

Need a live UDP echo Server IP and port

I require to test my UDP program using echo server. I have tested this application in LAN but now I require it to test it in Internet. Is there and globally recognize freely available well known ...
2
votes
0answers
29 views

Are DNS server responses categorized as “ESTABLISHED” by iptables? If so, why? [duplicate]

CentOS 5.x I'm trying to confirm which specific rule in my iptables config is allowing return UDP traffic from my DNS server. I THINK, it's this one: -A RH-Firewall-1-INPUT -m state --state ...
1
vote
1answer
420 views

Does hole punching require a UDP rendezvous server Or could it be a TCP one?

I'm trying to get my head wrap around this issue... I would like to connect two users... Those users are already connected to a TCP server, which is aware of both public ip and connection TCP port. ...
0
votes
1answer
111 views

Set udp packet size limit

I have a CentOS server with a JAVA application that receive UDP data packets, it works all OK until the packet is bigger than 584 bytes, I read something about and seems to be a limit of UDP protocol. ...
1
vote
0answers
80 views

Firewall rejecting UDP “connections”?

I have a server that is aggregating logs from various other servers. It mostly works great, however from time-to-time (right after a reboot, but not all reboots) it will decide that various UDP ...
2
votes
1answer
488 views

How to force use of tcp instead of udp for rpcbind?

I'm trying to use tcp/111 for rpcbind under Debian Wheezy instead of udp/111. The portmap in Squeeze uses tcp/111 without any special configuration, but Wheezy fails. Even numerous sites (as well as ...
0
votes
0answers
16 views

udp expected behaviour not responding to test result

I have a local network topology that is structured as follows: three hosts and a switch in the middle. I am using a switch that supports 10,100,1000 Mbit/s full/half duplex connection. I have ...
3
votes
4answers
2k views

How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 ...
0
votes
0answers
276 views

UDP packets are not reaching iptables NAT table

I'm trying to redirect UDP incoming packets to port 4000 to another IP with iptables: iptables -t nat -A PREROUTING -p udp --dport 4000 -j DNAT --to-destination 192.168.100.20 Unfortunately they ...
2
votes
1answer
50 views

How to see log of apps taking specific port over period of time on Windows?

How can I see for specific time period, which app had bound some specific port in Windows? I am auto-starting my app with windows and I am bounding port 1200 as UDP packet receiver, but sometimes my ...
1
vote
1answer
429 views

UDP bandwidth calculation based on packet size, request rate and latency [closed]

I need to estimate the bandwidth for a measurement application to be written that uses UDP. I have a good sense of the numbers but am not sure how to put them together. I checked a few throughput ...
0
votes
1answer
127 views

forward snmptraps with snmptrapd to second host

I have a setup with snmptrapd listening on udp:162 to receive snmp traps. They are then processed on this host with snmptt. I am now in the need that I need to forward those traps additionally to ...
0
votes
0answers
81 views

Why are my multicast packet discarded?

I have two boxes and I have some issues when tcpreplaying a pcap full of multicast from one machine to the other. I see the packet incoming on the destination machine thanks to a tcpdump instance. ...
1
vote
1answer
76 views

Debian 7.4 drops UDP traffic randomly

I'm running Debian 7.4, KVM VPS with the latest updates. I'm getting UDP ports randomly closed for 2-10 minutes for no reason. I'm running gaming servers and the port tester shows the ports are ...
4
votes
2answers
1k views

Is OpenVPN UDP vulnerable to heartbleed?

Is OpenVPN UDP vulnerable to heartbleed? I need to decide if I'm going to rebuild some servers, but they are very carefully firewalled; 1194/TCP is one of the firewalled ports (yay whitelist!). ...
4
votes
1answer
246 views

How does an Access Point handle broadcast packets from the wired side?

I have an Cisco AP 1242AG autonomous AP connected to L2 switches. Let's say I have 100 wired devices each sending 2 broadcast UDP packets per second. Obviously these packets will reach the Access ...
-1
votes
2answers
104 views

How to handle an abuse complaint? [closed]

I have just received an abuse complaint from my hosting service: [2014-04-04 03:30:23 CET] [Timestamp:1396575024] [11717182.634230] Firewall: *UDP_IN Blocked* IN=eth0 OUT= SRC=My IP ...
1
vote
1answer
220 views

Does Azure support UDP Broadcast?

I am aware that Azure supports UDP, but does it support UDP broadcast? I am wanting to use the Jenkins Swarm plugin, which requires UDP broadcast for new slaves to join the master.
0
votes
0answers
44 views

tcpdump, display the data section

i am trying to display only the data section of an udp packet using tcpdump. In some other words, is it any way to filter the header section of the udp package? The below command sudo tcpdump ...
0
votes
0answers
45 views

Need to setup an intermediary to accept, alter and resend a UDP packet

Currently ApplicationA on ServerA sends a UDP packet to ApplicationZ on ServerZ several times throughout the day based on several triggers. The problem is that some of the data in that packet is sent ...
0
votes
0answers
75 views

opensips sever running fine and UDP connection cannot register but TCP connections works fine

Im a newbie to opensips and Centos/Linux. Recently installed opensips sever which running smoothly on TCP connections, but users cannot register on UDP connections. here my Log, have a look. Feb 26 ...
2
votes
2answers
1k views

Rate of UDP packet loss over WLAN

While testing something with TFTP I noticed lots of timeouts (and slow speed as result) when I used my WLAN - and no problems when using a network cable. A quick test program sending/receiving UDP ...
1
vote
3answers
3k views

Ubuntu Server attack? how to solve?

Something (Someone) is sending out UDP packets sent from our whole ip range. This seems to be multicast DNS. Our server host provided this (Our IP Address is masked with XX): Jun 3 11:02:13 ...
1
vote
1answer
349 views

rsyslog udp forwarding truncates at 2048 characters

Rsyslog on a RHEL 6 server is receiving messages locally on port 514 UDP. These messages are sometimes much larger than normal syslog message sizes. I am seeing rsyslog handle all of the messages ...
1
vote
8answers
878 views

Network monitoring solution [closed]

I have a big distributed system I need to monitor. Background: My system is comprised of two servers, concentrating and controlling the system. Each server is connected to a set of devices (some ...
0
votes
2answers
40 views

Suspect UDP traffic on lo interface

I'm monitoring the lo interface with iptraf and am getting a lot of movement in the following form: UDP (268 bytes) from 127.0.0.1:49254 to 127.0.0.1:49254 on lo This message appears on average ...
2
votes
3answers
3k views

Why isn't my ip helper-address helping?

I have a hub site with a Cisco 2811 and several remote sites, running a mixture of Cisco 851 and 871 routers configured for site-to-site VPN. I am in the process of adding DHCP scopes and DNS zones ...
1
vote
1answer
2k views

How do I increase UDP Recv-Q

I have a gigabit connection that is not fully utilized but I am getting packet receiving loss. When I do netstat, it shows the Recv-Q sometimes maxes out at 262656 during heavy traffic. Proto Recv-Q ...
3
votes
1answer
970 views

Reverse proxy for mixed tcp, udp, and http services

I'm building an architecture that will be hosting various services which individually maybe listening on a variable number of ports that could be mixed protocols. I want to map these services to ...
4
votes
1answer
700 views

HTTP, TCP, UDP and connectionless

I am a bit confused with HTTP lately. Some facts are that TCP can operate connection orientated or connectionless, this I understand. TCP though is connection-oriented while UDP is connectionless ...
0
votes
1answer
560 views

UDP port appears to be in use but is not shown in netstat or TCPView

I've encountered some strange behavior I don't understand. I'm installing software on a Windows 2003 Server. This software needs to bind to a specific UDP port an all TCP addresses in order to listen ...
0
votes
0answers
85 views

How can I allow UDP traffic over my SBS2011/Win7 VPN connection?

VPN Server: Windows SBS 2011 Client workstation: Windows 7 64bit Enterprise Machines in physically separate network (home & office) I am in the process of troubleshooting a problem where a ...