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.

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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, ...
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29 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 ...
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17 views

OpenVPN works internally, not externally [duplicate]

I have OpenVPN set up on an Ubuntu server, which is behind a router. The VPN is operating on UDP port 1194, which is set to ACCEPT on the server's iptables configuration, and forwarded to the server ...
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1answer
28 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 ...
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1answer
130 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 ...
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1answer
69 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 ...
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2answers
45 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 ...
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1answer
227 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 ...
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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 ...
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1answer
81 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. ...
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66 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 ...
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2answers
67 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 ...
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15 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 ...
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234 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 ...
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1answer
48 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 ...
2
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1answer
282 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 ...
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1answer
363 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 ...
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74 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. ...
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1answer
73 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 ...
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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!). ...
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1answer
210 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 ...
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2answers
98 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 ...
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1answer
196 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.
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1answer
115 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 ...
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42 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 ...
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43 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 ...
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68 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 ...
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1answer
313 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 ...
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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 ...
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1answer
910 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 ...
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1answer
497 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 ...
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73 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 ...
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1answer
102 views

How can I determine if my VPN is passing through UDP traffic?

I have an client application that is unable to connect with it's server counterpart over a VPN connection. Server is Windows SBS 2011, client is Windows 7 64bit Enterprise. Using Windows VPN client. ...
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284 views

UDP Overflow / UDP Drops on Standby Postgres Service

I am stumped trying to prevent an overflowing UDP buffer on a standby Postgres service. Any help would be most appreciated. Essentially a UDP buffer associated with the pg_standby process on my ...
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1answer
149 views

amazon ec2 does not seem to accept udp data

Am using ffmpeg to receive data on udp protocol on Amazon ec2 e.g. #> ffmpeg -i udp://0.0.0.0:2013 -f flv http://0.0.0.0:8090/live.ffm but there does not seem to be any packets received. for ...
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1answer
183 views

OpenVPN client opens a random UDP port?

We are noticing this on a number of our openvpn clients: [root@box ~]# netstat -tulpn | grep openvpn udp 0 0 0.0.0.0:53950 0.0.0.0:* ...
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1answer
290 views

UDP maximum segment size

Environment: I am writing a UDP client-server application. the path MTU between client and server is 1500 bytes (with only a wireless link between them, so this value is pretty much stable). My system ...
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179 views

How to forward UDP and TCP traffic from one IP to another

I have a server with two LAN cards installed. I have one server in U.S and one in India. I have created a GRE tunnel to route all traffic from the U.S Server to my Indian Server. My traffic has ...
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1answer
101 views

Loadbalance UDP traffic with session affinity and way to take servers in & out of rotation [closed]

What is the best way to go about load balancing UDP traffic among a whole bunch of servers, while keeping session affinity based on the users' IP? I need to also be able to take servers in and out of ...
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1answer
890 views

How do I add a broadcast IP to the loopback interface under os/x using ifconfig when my machine has no network? [duplicate]

I'm new to advanced network administration and I would like to do some testing with UDP broadcasting, so I need a broadcast address on my loopback interface. The machine is offline, in other words, ...
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2answers
126 views

What is the equivalent of 127.255.255.255 for OS/X machines so I can test broadcast udp packets without a network? [duplicate]

I am trying to test my program that makes use of broadcast UDP (not multicast!). In Linux, I can use the 127.255.255.255:64651 address and everything works beautifully, in other words, I send a packet ...
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1answer
244 views

UDP packet loss on Netgear GS110TP

I'm trying to flow data via UDP on two ports of a Netgear GS110TP switch, running the latest available firmware (5.4.2.9). However, I'm experiencing a small amount of packet loss, something like ...
2
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2answers
237 views

Load Balancing UDP traffic transparently

Are there any products (preferably open source) that can load balance UDP packets transparently? We need to scale our syslog servers and require the original source IP be kept intact. Alternatively ...
2
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1answer
3k views

OpenVPN Error : TLS Error: local/remote TLS keys are out of sync: [AF_INET]

Fist off thanks for reading this, I appreciate any and all suggestions. I am having some serious problems reconnecting to my OpenVPN client using Riseup.net's VPN. I have spent a few days banging my ...
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2answers
71 views

DNS over TCP not udp [closed]

A Network problem with ISP caused all UDP traffic to cease, but DNS still working though I think it is malfunctioning. How to prove for sure using software that my current DNS queries are resolved ...
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63 views

Internal IP leaked to the public network

I am a programmer and I have made a production server that resides on public IP and listens for UDP packets. The purpose of this server is to collect UDP packets from a huge sensor network. And also ...
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5answers
2k views

Can TCP and UDP packets be split into pieces?

Can TCP packets arrive to receiver by pieces? For example, if I send 20 bytes using TCP protocol, can I be 100% sure that I will receive exactly 20 bytes at once, not 10 bytes then another 10 bytes ...
2
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0answers
160 views

Why is qemu issuing a DHCP discover after it receives a DHCP offer

I'm having some trouble seting up network on qemu. I'm trying the easy option (user). The qemu command I run is this: ./qemu-xilinx/arm-softmmu/qemu-system-arm \ -M xilinx-zynq-a9 -m 1024 ...
2
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1answer
112 views

Cat a file(raw) to UDP at specific bitrate

I'm looking for a way to transfer a file over UDP at an specific bitrate. I can use netcat for example like this: cat file | nc -u 192.168.x.x 5000 And I use a custom application to listen at port ...
3
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2answers
528 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 ...