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• C, Linux: Receiving data from multiple multicast address on same port - how to distinguish them?

  - by Gigi

  2 vote down star I have an application that is receiving data from multiple multicast sources on the same port. I am able to receive the data. However, I am trying to account for statistics of each group (i.e. msgs received, bytes received) and all the data is getting mixed up. Does anyone know how to solved this problem? If I try to look at the sender's address, it is not the multicast address, but rather the IP of the sending machine. I am using the following socket options: struct ip_mreq mreq; mreq.imr_multiaddr.s_addr = inet_addr("224.1.2.3"); mreq.imr_interface.s_addr = INADDR_ANY; setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)); and also: setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &reuse, sizeof(reuse)); I appreciate any help!!!

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• Is 1-to-n multicast on the open internet reliable?

  - by Jeremy Dunck

  I'm a newbie at networking. I understand the concept of multicast, but was wondering if it's reliable on the open/public internet? It seems like sort of an edge case that different backbones or ISPs might intentionally break to reduce router load or generally segment the network for practical high-use applications. Is my fear reasonable? P.S. Follow-up question here: http://stackoverflow.com/questions/256125/best-tutorial-for-application-multicasting

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• IPv6 multicast addresses: Is the Group ID field effectively 112 bits or 32 bits?

  - by Jeremy Friesner

  Hi all, I'm trying to understand the rules for choosing an IPv6 multicast address Group ID, and the RFC seems somewhat inconsistent. For example, in RFC 2373 section 2.7 this diagram is shown: | 8 | 4 | 4 | 112 bits | +------ -+----+----+---------------------------------------------+ |11111111|flgs|scop| group ID | +--------+----+----+---------------------------------------------+ ... but then in section 2.7.2 it shows this: | 8 | 4 | 4 | 80 bits | 32 bits | +------ -+----+----+---------------------------+-----------------+ |11111111|flgs|scop| reserved must be zero | group ID | +--------+----+----+---------------------------+-----------------+ So my question is, are the upper 80 bits of the Group ID field usable or not? If they are usable, is it only under certain circumstances (e.g. when using non-Ethernet networking technology?) What problems should I expect to experience if I set these bits when multicasting over an Ethernet LAN?

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• Setting up ehcache replication - what multicast settings do I need?

  - by Darren Greaves

  I am trying to set up ehcache replication as documented here: http://ehcache.sourceforge.net/EhcacheUserGuide.html#id.s22.2 This is on a Windows machine but will ultimately run on Solaris in production. The instructions say to set up a provider as follows: <cacheManagerPeerProviderFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory" properties="peerDiscovery=automatic, multicastGroupAddress=230.0.0.1, multicastGroupPort=4446, timeToLive=32"/> And a listener like this: <cacheManagerPeerListenerFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory" properties="hostName=localhost, port=40001, socketTimeoutMillis=2000"/> My questions are: Are the multicast IP address and port arbitrary (I know the address has to live within a specific range but do they have to be specific numbers)? Do they need to be set up in some way by our system administrator (I am on an office network)? I want to test it locally so am running two separate tomcat instances with the above config. What do I need to change in each one? I know both the listeners can't listen on the same port - but what about the provider? Also, are the listener ports arbitrary too? I've tried setting it up as above but in my testing the caches don't appear to be replicated - the value added in one tomcat's cache is not present in the other cache. Is there anything I can do to debug this situation (other than packet sniffing)? Thanks in advance for any help, been tearing my hair out over this one!

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• Turn-based Client-Server Card Game - Unicast (TCP) or Multicast (UDP)

  - by LDM91

  I am currently planning to make a card game project where the clients will communicate with the server in a turn-based and synchronous manner using messages sent over sockets. The problem I have is how to handle the following scenario: (Client takes it turn and sends its action to server) Client sends a message telling the server its move for the turn (e.g. plays the card 5 from its hand which needs to placed onto the table) Server receives messages and updates game state (server will hold all game state). Server iterates through a list of connected clients and sends a message to tell of them change in state Clients all refresh to display the state This is all based on using TCP, and looking at it now it seems a bit like the Observer pattern. The reason this seems to be an issue to me is this message doesn't seem to be point-to-point like the others as I want to send it to all the clients, and doesn't seem very efficient sending the same message in that way. I was thinking about using multicasting with UDP as then I could send the message to all the clients, however wouldn't this mean that the clients would in theory be able to message each other? There is of course the synchronous aspect as well, though this could be put on top of the UDP I guess. Basically, I would like to know what would be good practice as this project is really all about learning, and even though it won't be big enough to encounter performance issues from this I would like to consider them anyway. However, please note I am not interested in using message oriented middleware as a solution (I have experience with using MOM and I'm interested in considering other options excluding MOM if TCP sockets is a bad idea!).

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• Multicasting Windows 7 Image

  - by LawnChairSkank

  I am trying to deploy some new machines with windows 7 for the first time in our computer labs. We used to use third party imaging software and then run sysprep after the image was copied(XP), but it seems you can't go that route with windows 7. We set up a new imaging server with the windows system image manager, but when we try to multicast the image it pretty much takes down our whole staff and faculty network. I heard you can turn on a multicast feature on our cisco switches to help with the issue, but that it also slows the switches to a crawl. Another idea we have tried was pulling the the computer lab switch off the main network and plugging the imaging server directly into the computer lab switch so the multicast doesn't take down our network, but it doesn't seem to work without being able to hit a domain controller. Is there a way to multicast without taking out the network? I feel like I am missing something... Thanks in advance

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• Is there Muticast routing support on a Cisco 3750?

  - by mrtechalot

  We have a switch (Cisco WS-C3750G-48TS) with only a C3750-IPBASE-M image (not a 'C3750-IPSERVICES-M' license). Is there any kind of multicast support here? All I need it to do is route multicast packets to an RP (ip pim sparse-mode). Do we really need the service (C3750-IPSERVICES-M) license/image?. The uplink switch is running C3750-IPSERVICES-M, but this switch doesn't seem to carry any ability to configure multicast on an interface.

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• How do I make my multicast program work between computers on different networks?

  - by George

  I made a little chat applet using multicast. It works fine between computers on the same network, but fails if the computers are on different networks. Why is this? import java.io.*; import java.net.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class ClientA extends JApplet implements ActionListener, Runnable { JTextField tf; JTextArea ta; MulticastSocket socket; InetAddress group; String name=""; public void start() { try { socket = new MulticastSocket(7777); group = InetAddress.getByName("233.0.0.1"); socket.joinGroup(group); socket.setTimeToLive(255); Thread th = new Thread(this); th.start(); name =JOptionPane.showInputDialog(null,"Please enter your name.","What is your name?",JOptionPane.PLAIN_MESSAGE); tf.grabFocus(); }catch(Exception e) {e.printStackTrace();} } public void init() { JPanel p = new JPanel(new BorderLayout()); ta = new JTextArea(); ta.setEditable(false); ta.setLineWrap(true); JScrollPane sp = new JScrollPane(ta); p.add(sp,BorderLayout.CENTER); JPanel p2 = new JPanel(); tf = new JTextField(30); tf.addActionListener(this); p2.add(tf); JButton b = new JButton("Send"); b.addActionListener(this); p2.add(b); p.add(p2,BorderLayout.SOUTH); add(p); } public void actionPerformed(ActionEvent ae) { String message = name+":"+tf.getText(); tf.setText(""); tf.grabFocus(); byte[] buf = message.getBytes(); DatagramPacket packet = new DatagramPacket(buf,buf.length, group,7777); try { socket.send(packet); } catch(Exception e) {} } public void run() { while(true) { byte[] buf = new byte[256]; String received = ""; DatagramPacket packet = new DatagramPacket(buf, buf.length); try { socket.receive(packet); received = new String(packet.getData()).trim(); } catch(Exception e) {} ta.append(received +"\n"); ta.setCaretPosition(ta.getDocument().getLength()); } } }

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• Force netsh/arp binding multicast IP addres with specific MAC address

  - by Olivier

  I would like to setup an binding from an IP address to a MAC address using netsh. Goal is to bond an IP address which is a multicast address (224.224.x.y) to a given MAC address (which is NOT the calculated one from the multicast IP address : 01:00:5e:X:Y:Z It used to work with Windows XP (was it a bug that used to be "perfect" for my needs?), but Windows 7/8/8.1 forces the MAC address to the calculated one instead of letting me put what I want! (http://nettools.aqwnet.com/ipmaccalc/ipmaccalc.php shows MAC address calculation for multicast IP address) Thus I'm doing the following. Listing existing mappings: netsh.exe interface ip show neighbors "Ethernet" Interface 12 : Ethernet Internet address Physical address Type 224.0.0.22 01-00-5e-XX-YY-ZZ static Then adding my interface mapping manually: netsh.exe interface ip add neighbors "Ethernet" "224.xxx.yyy.zzz" "00-80-EE-UU-VV-WW" Finally, listing again my mappings: netsh.exe interface ip show neighbors "Ethernet" Interface 12 : Ethernet Internet address Physical address Type 224.0.0.22 01-00-5e-XX-YY-ZZ static **224.xxx.yyy.zzz 01-00-5e-UU-VV-WW static** As you can see, the MAC Address of the second entry (the one I just made) has been dynamically replaced by the calculated MAC Address corresponding to my IP Address... Calculation is done as follow (and displayed in hexa): UU=(xxx-128) VV=yyy WW=zzz But I don't want that behavior. My IP address and MAC address cannot be changed, and I must associate them accurately. Does anybody know how to disable MAC address substitution/calculation in netsh? Thanks, Olivier.

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• Where are possible locations of queueing/buffering delays in Linux multicast?

  - by Matt

  We make heavy use of multicasting messaging across many Linux servers on a LAN. We are seeing a lot of delays. We basically send an enormous number of small packages. We are more concerned with latency than throughput. The machines are all modern, multi-core (at least four, generally eight, 16 if you count hyperthreading) machines, always with a load of 2.0 or less, usually with a load less than 1.0. The networking hardware is also under 50% capacity. The delays we see look like queueing delays: the packets will quickly start increasing in latency, until it looks like they jam up, then return back to normal. The messaging structure is basically this: in the "sending thread", pull messages from a queue, add a timestamp (using gettimeofday()), then call send(). The receiving program receives the message, timestamps the receive time, and pushes it in a queue. In a separate thread, the queue is processed, analyzing the difference between sending and receiving timestamps. (Note that our internal queues are not part of the problem, since the timestamps are added outside of our internal queuing.) We don't really know where to start looking for an answer to this problem. We're not familiar with Linux internals. Our suspicion is that the kernel is queuing or buffering the packets, either on the send side or the receive side (or both). But we don't know how to track this down and trace it. For what it's worth, we're using CentOS 4.x (RHEL kernel 2.6.9).

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• creating secure multicast with socat

  - by arash

  How we can create secure tunnels multicast with socat? Assume we have a list of ip address, CIDR network addresses that we want to create secure tunnel to them. I found this socat STDIO UDP4-DATAGRAM:224.1.0.1:6666,range=192.168.10.0/24 but I want a secure tunnel and different adds with net addrs I want to create script that give the IPs and net addresses and create secure tunnel ./myscript IP1 NetAdd1 IP2 NetAdd2 .... how can i send this parametersw to socat? Socat multicast hasn't any limits? Thanks for your help

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• kvm -net only passing broadcast, multicast, and guest destination traffic

  - by user52874

  Figured this out just last week, but I can't find it now. Even printed it out. Can't find that either. Frustrating...so...help! Configured a 'monitoring' nic on a kvm guest (running 'Security Onion, if it matters). I read (somewhere) that the default nic configuration for a kvm guest is to only pass broadcast traffic, multicast traffic, and traffic with the guest's mac as a destination. There is an option to override this behaviour, and pass all traffic. It's something like --mac-filtering=no, or --mac-restriction=no, or something like that. Worked beautifully. Does this look at all familiar to anyone who can clue me in to the exact option syntax? thx.

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• Windows Network Load Balancing on ESX Cluster with Dell PowerConnect stacks

  - by dunxd

  We recently switched out our Cisco 6500 core switch for a pair of Dell PowerConnect 6248 stacks. Since then, our Network Load Balanced Sharepoint, which runs on two virtual machines on an ESX cluster has been behaving very poorly. The symptoms are that opening and saving documents stored in sharepoint takes a very very long time. There are no errors showing up on the Sharepoint servers or SQL server, just a lot of annoyed users. Initially I thought there was no way NLB could cause this, but as soon as we repointed the DNS records for our intranet to the ip address of one of the web front ends, the problems disappeared. We suspect there is an issue related to multicast in the Dell configs - NLB is configured for multicast, but not IGMP. Has anyone got a similar set up to us and fixed this sort of issue? Sharepoint on VMware ESX, with Dell PowerConnect switches.

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

  - by JohnPristine

  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 to 127.255.255.255:64651 and multiple clients listening on that port get the packet. A real broadcast example! Unfortunately on my OS/X machine (Mountain Lion) the same example does not work. Is there any way I can get 127.255.255.255 to work on mac machines? Any other solution to get broadcast working on my mac machine without a network? Note: It has to be broadcast, not multicast.

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• MPEG2-TS streaming: UDP or RTP?

  - by Juan Jose Polanco Arias

  Hello I'm working on an IPTV streaming server in Linux (Ubuntu Server 12.04 LTS) that has a DVB-S/S2 card to obtain satellite channels. Then with MuMuDVB I map all channels in the transponder to a multicast group, for multicast transmission. Now for the MuMuDVB software I can either use UDP for transmission or I can add the RTP header. I was wondering what would be the most convenient for MPEG2-TS because I've heard that RTP is used primarily for MPEG4, but It's also said that RTP can be used for MPEG2-TS. Thanks for your help.

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• Multiple network interfaces and UDP packets distribution

  - by Robert Kubrick

  I have a Linux server with 2 1Gb network interfaces eth1 and eth2. If I start 2 clients listening to the same multicast address and each client connects through a different NIC (say client 1 listens to the multicast through eth1 and client 2 through eth2), then client 2 gets duplicate UDP packets. If both clients use the same interface eth1 on the other hand, both clients work fine. I have already tried to set arp_filter and proxy_arp to 1 (arp flux issue) but it hasn't solved the issue. Is this a Linux kernel problem? Or is there another way to setup the interfaces correctly?

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• How can I redirect/forward all the UDP/TCP traffic on one interface to another interface in OpenWrt

  - by Sina Sou

  I am new to networking and I have a measurement device (D) that periodically sends all its readings over few UDP multicast sockets (with different multicast IP addresses and different port numbers). That device even listens to a TCP socket simultaneously to modify its configuration on port 7234. Since the device has just a Ethernet interface for communication and I want to make it work wireless, I decided to use a very small wireless open-wrt based router that attaches to the device (D) and redirect/forward all the network traffic(Both UDP/TCP) to the router wireless interface. In order to simplify the problem assume that the Device (D) establishes following sockets (at the same time) UM_SOCK1: UDP mcast socket on 239.1.2.3 port# 50620 UM_SOCK2: UDP mcast socket on 239.1.2.4 port# 50640 TC_SOCK3: TCP DHCP/STATIC ip address 192.168.1.200 port 7234 And (D) is connected to Open-Wrt router (R) via interface en01 (Ethernet) the router has it own wireless interface on (wlan0) I want all the traffic from interface pass through wlan01 and vice versa (bi-directional) en01 <---- wlan01 What would be the minimum iptables or ... commands that I need to make this possible? Even I am wondering if traffic directing can be made easier like if the direction is not going to be based on IP addresses(not desired if the device is connected via DHCP) I would rather redirection to be Interface(en0) based or on MAC address (The best solution since my device has unique MAC address)? Thanks

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• nameserver spoiling avahi multicast name resolution of .local domain

  - by Doug Coburn

  After trying to ping a machine on my local network, I noticed that I was trying hit address 66.152.109.24. This is an external public address. Resolution should have occurred via avahi mDNS. I ran dig to see how the name resolution worked and my quest/centurylink name server was retuning results for my .local domain queries! I tried a random name and got the same ip address result. $ dig jakdafj.local ; <<>> DiG 9.8.1-P1-RedHat-9.8.1-3.P1.fc15 <<>> jakdafj.local ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58410 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;jakdafj.local. IN A ;; ANSWER SECTION: jakdafj.local. 10 IN A 66.152.109.24 jakdafj.local. 10 IN A 204.232.231.46 ;; Query time: 104 msec ;; SERVER: 205.171.3.25#53(205.171.3.25) ;; WHEN: Sat Mar 24 20:40:17 2012 ;; MSG SIZE rcvd: 63 Am I missing something or is my DNS name server at 205.171.3.25 corrupted?

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• Ganglia multicast with clustering

  - by luckytaxi

  Let's say I have two hosts. One acts as the server where gmetad and a local gmond resides. It also has the web interface. I then have a client that only has gmond configure as follows. Anyways, everything works fine if i remove the mcast_join line from the udp_recv_channel If I leave it as is the UI doesn't show any hosts. I'm following the quick start guide found here In my gmond.conf file i have the following. udp_send_channel { mcast_join = host1 port = 8661 ttl = 1 } udp_recv_channel { port = 8661 retry_bind = true mcast_join = host1 bind = host1 } In my gmetad.conf file i have. data_source "Infrastructure" host1:8661 host2:8661

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• Multicast Prblem in Linux Red Hat server

  - by Uma Kant Verma

  I am facing a very strange behavior on my server. I am using a linux cluster.On fail over server my broadcast application halts after 5 minutes.But it is working fine on Primary server. My application process listening on port and send broadcast.It is working 5 mins after that it wait on socket for further packets but it didn't receive anything. Same process is working fine at Primary server. Plz help me.

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• Pushing Large Files to 500+ Computers [closed]

  - by WMIF

  I work with a team to manage 500-600 rented Windows 7 computers for an annual conference. We have a large amount of data that needs to be synced to these computers, up to 1 TiB. The computers are divided into rooms and connected through unmanaged gigabit switches. We prepare these computers ahead of time with the Windows installation and configuration, plus any files that we have available to us before we send the base image in for replication by the rental company. Every year, we have presenters approach on site with up to gigs of data that need to be pushed to the room that they will be presenting in. Sometimes they only have a few files that are small sizes, such as a slide PDF, but can sometimes be much larger 5 GiB. Our current strategy for pushing these files is using batch scripts and RoboCopy. For the large pushes, we actually use a BitTorrent client to generate a torrent file, and then we use the batch-RoboCopy to push the torrent into a folder on the remote machines that is being monitored by an installed BT client. Often times, this data needs to be pushed immediately with a small time window. We have several machines in a control room that are identical to the machines on the floor that we use for these pushes. We occasionally have a need to execute a program on the remote machines, and we currently use batch and PSexec to handle this task. We would love to be able to respond to these last minute pushes with "sorry, your own fault", but it won't happen. The BT method has allowed us to have a much faster response time, but the whole batch process can get messy when there are multiple jobs being pushed. We use Enterprise Ghost for other processes, and it doesn't work well in this large of scale, plus it is really quite expensive for a once-a-year task like this. EDIT: There is a hard requirement that the remote machines on the floor are running Windows. The control machines do not have a hard OS requirement. I would really like to stay away from Multicast because of complications with upstream routers. Is Multicast or BitTorrent the better way to go on this? Is there another protocol that might work better?

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• relational databases and multicast messages

  - by xRobot

  I have read that relational databases are a terrible way to do multicast messages like twitter. So twitter saves every tweet only one times and then retrieve its in every stream ? or saves every tweet in every users's stream ? I want to know why relational database ( like mysql or postgresql ) doesn't good for twitter-like application.

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• Ruby IpV6 Multicast Sending and Receive

  - by Francesco Vollero

  Hi, as object i'm tring to create a client and server scripts in order to send and receive multicast packages over IPv6. In IPv4 everything work as well, but i cannot figure out how to change it in IPv6. I start as basis from Multicasting In Ruby but seems ff02::1 isnt good for MULTICAST_ADDR. Thanks in advance.

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• Is it possible to test multicast using the emulator

  - by CarlosF

  Is it posible tu test a multicast application (e.g. client-server protocol) using the emulator? if so, any reference to an example? I wrote a simple client-server application and execute them on the emulator but it seems nothing is sent/received. Thanks!

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• X11 screencasting multicasting solution

  - by Metiu

  I need to multicast an x11 application window to multiple (sai 100) clients in a lossy (wireless) environment. Right now, I was able to do it through screen grabbing (vlc) and h264 compression, but there should be a cleaner solution, something along the lines of a multicast NX session. Is there anything which could work with some glue, or should I build something for the purpose? Thanks

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