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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Why would a university block incoming UDP traffic with destination port 53?

From my understanding DNS uses UDP and port 53. What undesirable things could happen if incoming UDP packets to port number 53 weren't blocked? UPDATE: Packets originate or are destined to the ...
3
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3answers
6k views

Netcat UDP File Transfer?

Is there any way to send a file (picture or video) using Netcat and UDP. It defaults as TCP, but I would like to send using UDP. I tried simply adding -u to the nc command, but that didn't work. Here ...
3
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2answers
3k 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 ...
2
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0answers
37 views

How to use an IPv6 Edge router in an IPv4 network?

Background I have the following set-up: I use 6LOWPAN (IPv6 implementation in IEEE 802.15.4) on my sensor link that have IPv6 addresses (stateless) as aaaa::xx/64 It uses RaspberryPi (RPI) as an ...
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0answers
17 views

How to make svlogd send logs via UDP

I am currently using runit + svlogd for supervising some applications, but when deploying to multiple machines, I have the need to centralize/unify the logs in a single place in order to simplify ...
0
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1answer
15 views

udp broadcast on port 25860

I used wireshark on my local network (to test it), and i noticed that there is a lot of udp packets send one broadcast, and the majority is coming from only one host. Theses udp packets are send on ...
0
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2answers
2k 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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0answers
10 views

UDP destination address during port forwarding?

I have setup a connection using Qt in the LAN, PC1(192.168.1.195) will send UDP packets to PC2(192.168.1.201) with no problem. But now, PC1 and PC2 are now working under different routers. So now PC1 ...
2
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3answers
2k views

Troubleshooting UDP multicast on Windows

I'm a programmer, not a system adminstrator, so please forgive my administrative naivete. My software, written in C#, relies on UDP multicasting. One machine, the server, streams events to an known ...
3
votes
1answer
680 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 ...
3
votes
1answer
1k 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 ...
4
votes
1answer
107 views

udp packet delays in my dedicated WIFI network - can i force UDP nodelay over wifi?

I have a dedicated app and network development for passing UDP packets over a wireless network. The totality of the network is a PC (Mac OSX or Linux) which sends the packet-->router/AP-->WIFI ...
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votes
2answers
9k views

Higher rmem_max value leading to more packet loss

The rmem_max Linux setting defines the size of the buffer that receives UDP packets. When traffic becomes too busy, packet loss starts occurring. I made a graph showing how packet loss increases ...
2
votes
1answer
1k 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. ...
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votes
1answer
75 views

What are the ports needed for L2TP VPN on Mac OS X Server 5.0.15?

I'm configuring a Mac as a server with a VPN service. So, I opened the ports listed as used by VPN in Apple documentation: UDP 500 -> 500 (+ESP and AH) UDP 4500 -> 4500 Any UDP -> 1701 (I got to ...
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0answers
11 views

CentOS Drupal Site/Domain Sending UDP Attacks on Different IPs [duplicate]

My Drupal 7 site is hosted on a Cent-OS 6.5 VM. The hosting service provider notified me about an malicious activity on site and site is sending UDP packets on different IPs. Following is data ...
5
votes
2answers
126 views

How to allow UDP broadcast between interfaces on a Cisco ASA 5506-X

I have a CISCO ASA 5506-X with 4 configured interfaces and a set of access-lists etc. It is configured via CLI and is running in routed mode, not transparent. Everything is running well, but now I ...
13
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6answers
6k views

Solution to route/proxy SNMP Traps (or Netflow, generic UDP, etc) for network monitoring?

I'm implementing a network monitoring solution for a very large network (approximately 5000 network devices). We'd like to have all devices on our network send SNMP traps to a single box (technically ...
1
vote
1answer
37 views

Can't connect to python server on LAN

So I have this python server which just returns the uppercase sentence which came as a input: from socket import * serverPort = 12000 serverSocket = socket(AF_INET, SOCK_DGRAM) ...
5
votes
5answers
6k views

How to list all requests to udp sockets?

I'm operating a couple of server daemons that use udp to communicate with large number of clients. How do I find and list out all the active udp "connections" that are talking to the servers in order ...
0
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0answers
13 views

Packets not being delivered to application

First of all sorry if this is not the right place. So... I have a problem. I'm working on a linux board (the distro is created with yocto, kernel is 3.10.17). I have several network interfaces (WWAN1 ...
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0answers
29 views

netcat UDP port test response issue

I am running a game server on a Windows Server 2008 VPS/VDS through port 12203. I want to be able to automatically restart the game server exe file if it crashes. So, my strategy is to use netcat to ...
0
votes
1answer
31 views

Why are duplicated UDP packets being dropped 10 out of 11 times by this iptables configuration?

I am trying to duplicate UDP packets flowing to port 50007 on an Internet address from devices on a local NAT network (192.168.12.0/24) with the intent of processing them locally (on ...
0
votes
2answers
63 views

How to connect a client behind a NAT router to an Asterisk server behind a NAT router?

I have an asterisk setup on a server. The local IP address is 172.22.9.200 and extenal IP address is 75.45.185.100. My client device is an android phone that is connected to a router and it which ...
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2answers
50 views

Does UDP includes of source address?

Both UDP and TCP does not include source address, but how does it say UDP IP spoofing is easier than TCP? For example, the following webpage also says about UDP vulnerability. "Unlike TCP, UDP does ...
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1answer
31 views

What does the following UDP connection mean? [closed]

What does the following entry mean? Is that mean someone has connected to the server from this IP or somthing else? Nov 23 15:33:54 www-prod-2 snmpd[1573]: Connection from UDP: ...
2
votes
2answers
837 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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vote
2answers
340 views

Strange UDP/TFTP Problem

My TFTP client only seems to be getting responses from the TFTP server to its RRQ (download requests) if I watch the traffic in wireshark. If I shut down wireshark (running on the TFTP server), the ...
13
votes
6answers
41k views

Testing UDP port connectivity

I am trying to test whether I can get to a particular port on a remote server (both of which I have access to) through UDP. Both servers are internet facing. I am using netcat to have a certain port ...
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0answers
35 views

TCP and UDP ports usually blocked [closed]

Which are TCP and UDP ports most likely to be blocked? I refer especially to the client edge of the network. To start I guess SMTP (25), SIP (5060) for TCP, Traceroute (33434) for UDP.
3
votes
2answers
1k views

Load Balancing UDP traffic transparently [closed]

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 ...
18
votes
4answers
14k views

What is the “in-the-wire” size of a ethernet frame? 1518 or 1542?

According to the table here, it says that MTU = 1500 bytes and that the payload part is 1500 - 42 bytes or 1458 bytes (<- this is actually wrong!). Now on top of that you have to add IPv4 and UDP ...
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0answers
58 views

UDP Port Forwarding Error: channel 2: open failed: connect failed: Connection refused

My situation is as follows: I have currently trying to have a program between two Hosts send UDP packets over a SSH Tunnel. There is also a host intermediate between the two hosts. Note Server01 ...
1
vote
1answer
37 views

iptables accept specific packet id

I want to allow only packets with a specific id (identification field), for example packets with id=3 are accepted and others dropped. And I want to do the same thing with the offset, so for example ...
0
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0answers
68 views

How to prevent outgoing UDP flood

I've been googling for hours now but can't find a sure or helpful answer. I need to disable high-volume outgoing UDP from my server. I'm trying to configure APF because of the RAB functionality, but ...
0
votes
1answer
16 views

Does STUN work on majority of NATs?

I've been largely ignoring STUN protocol as noise for a while, but I keep encountering it here and there, and I'm wondering of it's general usability. If I understand it right, STUN is only useful if ...
7
votes
2answers
232 views

Windows Server 2012 - RDP over UDP not working

I have a Windows Server 2012 (not R2) machine, hosted within Hyper-V virtualization with RD Session Host & RD Gateway installed. It is used to run a desktop GIS application. The performance over ...
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2answers
80 views

Any protocol used by TRACEROUTE ? ICMP or UDP [closed]

Any protocol used by TRACEROUTE : ICMP or UDP or IP ? Or use them all : Encapsulation ?
2
votes
1answer
80 views

difference between local port range & UDP sending port using dig on Debian nameserver resolver

When i go to my local port range on Debian 7, i can see that my ephemeral port range is: cat /proc/sys/net/ipv4/ip_local_port_range 32768 61000 My /etc/sysctl.conf is empty. Normally that would ...
1
vote
4answers
2k views

How can I reject all incoming UDP packets except for DNS lookups?

I set my server to reject ALL incoming UDP packets, to prevent UDP floods. However, I was told that because I use my own domain and server for my nameservers, this can cause some problems. How can I ...
1
vote
2answers
154 views

Can't change source IP address (to floating ip) for udp outgoing packages

I'm having trouble getting a cluster to work using pacemaker and corosync. Here is my hardware configuration: Network: 192.168.3.0/255.255.255.0 Gateway: 192.168.3.1 node1 (Ubuntu Server 12.04 x64) ...
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3answers
4k views

How to measure and minimize UDP packet loss

I sometimes face voice break when calling through a VOIP application. Since all VOIP applications uses UDP for data transmission, is there any tool in Linux to measure the amount of packet loss and ...
0
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0answers
34 views

Colasoft Packet Player with Loopback-Adapter - Cannot recieve UDP-Packages

I have some problems with Colasoft Packet Player. I am trying to send the UDP-Packages over a Loopback-Adapter (Windows 7, I want to send and receive them over the same computer) and to read them with ...
4
votes
2answers
22k views

Verify connectivity to a server on a UDP port

I want to know if a HP-UX machine can communicate to a remote machine (which I don't have control over) on a particular port using UDP. I tried telnet, but it doesn't look like it supports UDP. I ...
5
votes
3answers
11k views

Iptables: “-p udp --state ESTABLISHED”

let's look at these two iptables rules which are often used to allow outgoing DNS: iptables -A OUTPUT -p udp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A ...
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0answers
125 views

UDP packets seen on interface level but not delivered to application on RedHat

I have a problem with receiving UDP traffic on a RHEL6 server. When capturing the traffic with tcpdump, the packets are visible (checksums are correct, the destination IP and MAC match the machine's ...
0
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2answers
42 views

SMB / CIFS / Samba Connectionless or Not whilst transfering files?

I have been researching this for a bit, but I have been getting conflicting answers, does samba, from my gatherings, SMB runs on ports TCP & UDP 137-139 & 445. But I have no idea therefore ...
1
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1answer
342 views

Firewall UDP Flood Dos/DDoS

Recently I have been suffering from what appears to be a UDP query flood attack. I am looking for a way to block the attack using a software firewall such as iptables, this should be possible, as ...
2
votes
1answer
53 views

I need to REJECT first incoming UDP packet by srcip

Im currently under attack by spoofed udp packets. Every spoofed ip trying to send just 1 udp packet in 30sec. But there is tons of ip. I need to drop first packet. But if same srcip in 30sec sends ...
1
vote
1answer
42 views

Dest host dont accept UDP when there is no route to source

I have three hosts with following config: Host A: IP:192.168.1.1/24 Host B: IP:192.168.1.2/24 Host C: IP:192.168.3.1/24 Everything happens on CentOS 6, and all interfaces are VLAN tagged (if it ...