Ubuntu Networking :: Unable To Receive Multicast?

Jun 23, 2011

For the last couple of days, I've been unsuccesfully trying to receive multicast packets on Ubuntu Server 11.04, and seen some strange things along the way. The program i use to test this, is basically http://www.scribd.com/doc/38224328/mcreceive-c.Now the network has been configured to forward me the multicast packets, regardless of the joins. So tcpdump shows me:

15:16:11.308952 IP > UDP, length 1400


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Fedora Networking :: Unable To Receive Multicast Data

Jun 13, 2010

I have just set up an FC 13 box for a small network application. At the core, the application is supposed to receive some data over a multicast on my local network. However, for some reason, I am not being able to receive any multicast data on this machine. Other machines, on the same network (connected on the same layer 2 switch) are receiving the multicast just fine. I have tried the following things:

1. ensure that I am joining the multicast on the correct interface: the machine has only one ethernet card. Also, after starting my application, I use netstat -g to check for group membership. The multicast subscription shows up fine.

2. ensure there is no error in the program: the program works fine on my person linux machine

3. ensure that the multicast is actually available: it is available on all other local machines. I also wrote my own small broadcaster. data from this broadcaster (running on the same box) is available to other machines but not to my own listener program.

4. no firewall/filtering settings on the layer2 switch

5. TTL setting on the broadcast: have tried changing it from 1 through 5 with no effect. Note that even if the broadcast is coming from the same machine, my machine does not pick it up while other machines on the network do so.

I suspect this has to do with some settings on the network card itself. Below is the output of /sbin/ifconfig on the card:

eth0 Link encap:Ethernet HWaddr 00:08:A1:67:BBA
inet addr: Bcast: Mask:
inet6 addr: fe80::208:a1ff:fe67:bbca/64 Scope:Link


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Networking :: Cannot Receive UDP Multicast Packets From Windows

Dec 10, 2008

I've got an application that compiles in Windows and Linux and is using UDP multicast to communicate. I'm running it on a Windows machine, a Linux machine and a small board (Gumstix) that is running Linux as well. The Windows and Linux machines have no problems sending/receiving packets with each other. The Gumstix and Linux machines have no problems sending/receiving packets with each other. The Gumstix can also send/receive packets with two instances of the application both running on the Gumstix.

But when running on the Gumstix I can send udp multicast packets to Windows, but cannot receive them. (It works if I do point to point with a known IP port#, but not multicast.) I can run tcpdump on the Gumstix and see the packets, but they are not being received on my socket. Here's what tcpdump (running on the Gumstix) outputs when sending the same packet from different sources. Notice the IP header ID and flags (don't fragment) are different when coming from Windows.

WINDOWS to Gumstix
-7:-45:-2.015784 IP (tos 0x0, ttl 15, id 35331, offset 0, flags [none], proto: UDP (17), length: 444) > UDP, length 416

-7:-43:-38.451991 IP (tos 0x0, ttl 15, id 0, offset 0, flags [DF], proto: UDP (17), length: 444) > UDP, length 416

-7:-33:-10.955608 IP (tos 0x0, ttl 15, id 0, offset 0, flags [DF], proto: UDP (17), length: 444) > UDP, length 416

I've tried everything I can think of to get this to work but am not getting anywhere. Also I'm pretty inexperienced when it comes to Linux. Anything I could try to be able to receive udp multicast packets from Windows?

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CentOS 5 Networking :: Can't Receive The Multicast Data

Mar 27, 2009

I'm trying to receive data that is being broadcast on address,,, ports are 1201, 1202, 1203, 1204 respectively. I can see the data using wireshark but can not get my program to receive the data. all firewalls are shutdown. iptables is not running, i've set net.ipv4_icmp_ignore_broadcasts = 0 and still no luck.

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Ubuntu Networking :: Intermittent Connection With Bcm4312 - Unable To Send Or Receive Any Data For 30 Seconds

Jul 31, 2010

I have a Dell laptop with a bcm4312 wireless card. Every once in a while though, the laptop is unable to send or receive any data for 30 seconds. The connection is not dropped, and nothing shows up in any system logs. Both the wl and b43 drivers have this problem, but it works fine under vista.

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Ubuntu Networking :: Not Able To Get Multicast Working

Sep 1, 2010

I have several multicast data feeds that I'm trying to connect to using a minimal server install of Ubuntu as a VM on a VMWare ESXi server.I have another VM on the same server running Solaris that can connect with no issues to the incoming multicast stream.

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Networking :: Multicast With More Than One Network Interface?

Jul 30, 2010

If I have set up 2 network interfaces on a box, if I started sending multicast traffic, it will go out through both interfaces? Or is there a way to control through which interface it will go out?

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Networking :: Converting IP Multicast To MAC LLC Broadcast

Mar 5, 2010

This is not a linux specific question more of a general network issue with the hope that someone may have already done this under linux.My problem:I have a red hat linux machine transmitting IP multicast packets onto an ethernet gigabit network (cisco switch).Wireshark (running on a different red hat linux box confirms packets on network.

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Ubuntu Networking :: LTSP Server - Routing Multicast Communications?

May 16, 2010

I've just set up an LTSP server, with all its clients on a separate subnet to my main network - the main network is 192.168.1.x, and the LTSP clients are all 192.168.2.x. My LTSP server has 2 NICs, one on each network, and is merrily forwarding normal IP traffic from the clients to the rest of the network. I have a client/server application that has a server on one machine, and clients locate and attach to it using multicast protocols. The server is on the main network, and any other machines on the network can locate and talk to the server quite happily. The LTSP clients, however, cannot - I assume because the multicast communications aren't being forwarded by the LTSP server. How I can get this working?

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Networking :: Multicast UDP Packets Lost In Kernel

Jul 29, 2010

We have a high speed udp multicast connection. There are about 37 multicast groups and average incoming rate via the connection is about 20000 pkt/sec and peak 40000+ pkt/sec. Each packet is about 100-300 bytes. And there are 6 busiest multicast groups generating 80% of the traffic. No significant outgoing traffic via that interface. The problem is that, if our heavy-weight application create 37 sockets for all the groups, the packet loss become quite frequent. but if we create the 6 sockets for the busiest groups, the packet loss drops to 1/10 of the original level. We can confirm that the lost packets DO arrive in our box because a light-weight recorder on another box on the same ethernet segment can see the lost packets when listening to the same groups. If we start another heavy-weight application for the rest groups (31 groups ) on the same box, the packet loss just come back to the original level.

The packet loss happens not only to the heavy-weight application but also the light-weight recorder running on the same system. that is, the loss is system wide. The socket kernel buffer are all 4MB max and did not observe system buffer overflow. It seems the number of sockets listening to the same multicast group have the most negative impact on packet loss. And the higher traffic have a far less impact on packet loss than the number of sockets. It also seems that there is some limit in the kernel that when socket number are reduced under, the packet loss can significantly ease. How can I further diagnose the problem? Our system is RHEL 5.3 32bit i386, Xeon 2.9GHZ 16 Processors, 32GB memory. Two broadcom giga netowrk card and 6 Intel GIGA NIC, and only one interface card has so much traffic.

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Feb 5, 2008

I'm working on a realtime-audio application, which should be capable to receive RTP packets via multicast addresses. App did work fine till I switched from 2.6.22 to kernel 2.6.24 (because of hwmon support for VIA EPIA LT15000AG)

With kernel 2.6.22 I had no problems, I'm using almost identical .config
Also tried kernel 2.6.24-rc5, same problem.
Tried it on two different boards (diff. NIC's, cpu's mem, etc ..)

I'm using the same setsockopt with IP_ADD_Membership as before for all interfaces. But now my app does not receive any multicast packet ! Strange thing is, as long as tcpdump is running, the app (and tcpdump) get the multicast packets, but if i stopp tcpdump, my application at the same moment gets no more multicast packets. I can see with netstat -g the joined MC-address (if app is active) multicast route is set up properly. I'm using VLAN (VLAN packets routed to eth0.3).

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Networking :: Combining Multiple Interfaces With Multicast?

Apr 1, 2010

I have 4 interfaces, dvb0_0 - dvb0_3. Each one has a multicast stream coming in on it. The program I am using to decode these streams only accepts one interface though. How can I "combine" so that the program, listening on 1 ip can get all 4 streams? they are on groups

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Networking :: Join Multicast Group In Ipv6?

Jul 29, 2011

In the ipv4 code i was using "ip_mc_join_group()" to join the multicast group. but i cannot find a similar function for ipv6 i have found one ipv6_sock_mc_join() but this function is not available for use with my module as it is not exported.

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Networking :: Receiving Multicast On Multiple Interfaces?

Jul 9, 2010

I am trying to run some benchmark tests for multicast. What I want to do is have one system send multicast packets and another receive it on all it's interfaces (eth0-eth3). Whenever I run receiver on more than one interface I get echo effect (if I receive on x interfaces then I get same packet x number of times). Is this how it is supposed to behave? It does not make any difference whether I use loop-back or not. I have set SO_REUSEADDR to yes. I run separate instance of receiver on each interface. I am doing this on RHEL5 systems.

# uname -r

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Networking :: Mapping Ethernet Multicast Address?

Nov 23, 2010

have a doubt about the multicast address.I have read that IP and ethernet multicast address have the same last 23 bits. While an ethernet multicast address always starts with 01:00:5E. Changing the last 23 bits of the IP address into hexadecimal form and "adding" them to the first 24 bits we find the ethernet address but what about the missing bit??? For istance I have: = 11100110.00001011.01101111.00001010 So converting the last 23 bits I have b:6f:a The final ethernet address will be 01:00:5E:b:6f:a . And what about the missing bit?

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Ubuntu Networking :: Connecting To The Internet Or Recieve The Multicast Streams From The Iptv

Jan 23, 2011

I got a server setup with three nics

eth0 = wan
eth1 = lan
eth2 = iptv (multicast)

When I have my IPTV inserted in the computer I am either having problems connecting to the internet or recieve the multicast streams from the iptv. I do get a valid ip on both the WAN and IPTV, but I am having problems getting them both to work at the same time.

eth0 Link encap:Ethernet HWaddr 00:14:d1:1d:72:39
inet addr:94.xx.xx.63 Bcast: Mask:
RX packets:2180753 errors:0 dropped:0 overruns:0 frame:0


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Networking :: Lost Multicast Packets - Never Reach To Destination

Oct 3, 2008

I have a set of servers. Each of the servers has two IP addresses. The one IP connects it to the company LAN and the other creates a LAN between them for sharing database access and creating backups in order to minimize unnecessary traffic on the LAN. One of the servers is on one network and the other 4 are on another network. Something like this:

Gateway External Internal
Router --- --- (SERVER 1) --+
| |
+------ -+- (SERVER 2) --+
| |
+- (SERVER 3) --+
| |
+- (SERVER 4) --+
| |
+- (SERVER 5) --+

Access from both the External and Internal interfaces work without any issue. Each of the servers has a UDP Multicast client/server running. This periodically sends out packets informing the others of system health and that it is still running. These packets need to go out on the Internal interface. Currently the packets are going out on the External interface and not the Internal interface. The network on the External interface does not allow multicast and all packets are dropped never reaching the destination. Only one gateway (default) is configured for each server pointing to the gateway on the external interface. There is no gateway configured on the Internal side. I think I need to add a gateway on the internal side to get this to work but as it is not connected to another router I am not sure what this would be. I'm using Fedora 8 on all servers.

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Jan 7, 2011

How can I find out list of multicast addresses and port in use?"netstat -ng" only gives list of multicast addresses that have been joined, it does not give port number.I have several hundred servers running application that listens to several multicast addresses on different ports. I want to write an audit script and get the list of multicast address and port numbers.

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CentOS 5 Networking :: Can't Join Multicast Socket Group?

Nov 3, 2009

I have a PC connected by ethernet to a Galil motion controller card.I recently installed Centos 5.The Galil software for communicating with the card is reporting that it can't join a multicast socket group.The software used to work with another version of Linux.

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Ubuntu :: Unable To Receive Files Using Bluetooth?

Feb 13, 2011

pair my mobile with ma ubuntu laptop,, but i am not able to receive files.. infact am not able to start the Bluetooth manager also

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Ubuntu Security :: Cfs Encryption Gives: RPC: Unable To Receive

Aug 3, 2010

I want to create an encrypted directory using the cfs package. So far I've only been able to create the top directory. When I want to attach an encrypted directory using

cattach directory1 directory2

get the following message in command line:

RPC: unable to receive

When i look into my /crypt directory, nothing was added there. I have no idea what could be the problem. I use Ubuntu 10.04 LTS.

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Ubuntu :: Unable To Receive Mail In Evolution?

Nov 24, 2010

I can't seem to track down. In Evolution, I am unable to receive mail. I tried every configuration method I know and still no success. I'm even tried using a hotmail and verizon account settings with no luck.

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Software :: Postfix Unable To Receive Mail

Jun 26, 2010

I am using postfix in conjunction with the ispCP Control Panel. Here's some of the recent entries in maillog, when I try to send an email from my gmail address to an email address on this server (I underlined the email addresses).

2010-06-26T17:57:43.581654-04:00 li136-183 postfix/smtpd[30721]: fatal: No server certs available. TLS can't be enabled
2010-06-26T17:57:43.838633-04:00 li136-183 postfix/smtpd[30710]: warning: connect to Connection refused
2010-06-26T17:57:43.838677-04:00 li136-183 postfix/smtpd[30710]: warning: problem talking to server Connection refused .....

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Aug 6, 2009

I coundn't log in fedora anymore. Everytime i try, i receive the report "unable to open session".

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Jul 11, 2011

As per OpenNMS wiki documents, I configured everything for email notification of alarms. I am able to view notification under notifications, but I haven�t seen any mail alerts forwarded to recipient mail ID. Below are configuration files. Please review and suggest the required settings/actions. SMTP Server Details: SMTP Relay Server, OS: Linux

i also made the configuartion by opennms configuration material in opennms.org i edit the following conf file

1. javamail-configuration.properties file


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Mar 19, 2011

We are facing an issue with virtual users. We have configured postfix in Fedora 12. We are able to receive as well as send mails for the main domain users (i.e. example.com) but not able to receive virtual users mail (i.e. configured example2.com in main.cf and configured in virtual file as systems@example2.com useronly). We are receiving error message in outlook as 0x800CCC0F. Please guide us how to solve this issue.

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Aug 27, 2010

I installed NFS and portmap for export a folder to another PC. /usr/local. ftp is server's hostname and ws01 is client's hostname. I edited file /etc/exports with next text: /usr/local ws01(rw,root_squash) *(ro)

I restarted service portmap and nfs. From client, I try check connection with server with command: showmount -e ftp and result is: mount clntudp_create: RPC: Port mapper failure - RPC: Unable to receive

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Feb 12, 2009

I make an application on GNU/Linux which listening on a MULTICAST stream, so I open my unconnected socket, bind it on a MULTICAST address and a port, join the multicast group with the "setsockopt (IP_ADD_MEMBERSHIP)", then I receive datagram on my socket.

Now I've two different instances of the same application that run with their own MULTICAST address and port. And what I found strange is that, after a misconfiguration, I switch the ports, for example:

Emitting on and
Receiving on and

And my receiving part doesn't care about the MULTICAST address, it looks like the socket is listening on the port number only! I mean that the receiver [] take its datagrams from emitter [] and vice-versa!

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Mar 4, 2010

How do I make Ubuntu 8.04 receive an IP address as the machine is booting up, so I can access the machine through SSH without having to log in on the X Session.

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Ubuntu Networking :: Receive Files Via Bluetooth?

Nov 6, 2010

can't receive files via bluetooth whatever I do. When sending from mobile the file transfer dialog opens, but error pops up "Cannot connect to OBEX device". "Cannot copy file.. The remote system refused the network connection"I have

$ sudo dpkg -l |grep blue
ii blueman 1.21-2ubuntu1


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Feb 19, 2011

I use a sitecom wl-345 network usb adapter. But whatever i tried it don't recieve networks in range. When i type airodump-ng ra0 it won't work

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Ubuntu Networking :: Configuring Postfix Send And Receive Across Ethernet

Sep 27, 2010

I am would like to configure postfix to send and receive email across Ethernet (just for now). I have two machines with postfix installed both using Ubuntu 10.04 directly connected with an ethernet cable. I have successfully configured a machine to send email to gmail, however i have been unsuccessful in having these machines send email back and forth. I have been interested in setting up a little mail server at home and have just been trying some simple projects with postfix to start with. At this moment i am using ip addresses and am not concerned with using a dns server

machine A: has a fixed ip of, hostname = mail.me.com,
machine B: has a fixed ip of, hostname = mail.ubuntu.com
in the /etc/hosts file I map each hostname to ip address receptively (not sure if a good idea, but at this point I have been trying everything)

So I will execute from Machine B
echo "Here is a message" | mail -s 'Hello' cmd@[]

I currently get from mail.log timed out while receiving the initial server greeting. I get from mail.err valid hostname or network address required in server description #[]. Obviously when I run the mail command from cmd user i do not receive anything. I can receive mail from myself if from machine A, I sent an email using the command above. I would just like to send email from machine B and receive it on machine A via direct Ethernet connection. I have been through postfix documentation and have also read the postfix definitive guide and have had no luck.

Here is a recent main.cf as I have tried getting this to work (this is for machine A however, similar for B)

# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
myorigin = /etc/mailname .....

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Jan 6, 2010

I recently moved to Beijing and am having trouble with my apartment's wireless setup. My laptop can connect to any wireless network I find out in Beijing but not our home network. My Roommate has a mac laptop and has no issues connecting to our wireless router. It appears to connect but receive no signal, which is frustrating me to no end. Here is my spec list and the model of wireless router we are using.


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Oct 29, 2009

I have two situations here :

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2) I have my Nagios running on the linux box and BMC Remedy Server on the Solaris box. I have simulated a mail from Nagios to be delivered to the Remedy server. I snooped on port 25 on the Solaris box. I could see the mail reaching the box, but it is not being forwarded to the Remedy inbox.

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Jul 9, 2009

I have a C program which does.

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2. Send the UDP Request packet to the TFTP server.
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Is there a way to receive a notification from the Linux kernel on receipt of an ICMP packet to the created UDP socket.

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Mar 5, 2010

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Apr 24, 2010

I am using ubuntu 9.04. I have configured Evolution on my laptop, but it is not working.

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Apr 7, 2010

I am contemplating the use of DHCP options as a way of passing host-specific information to hosts that are booting disklessly from a network server. My intention is to have the DHCP client request certain options, and use the reply to configure the diskless hosts accordingly. The theory and rules behind all of this seem well documented on web sites such as die.net. However, the practical application of the protocol seems to be a lot less clear. What I am looking for is an explanation of what (existing, I hope) tool(s) are used, and how they are applied so that I can grab information from the DHCP server, and use it in userspace scripts or other programs. Specifically, my intention is to use a locally defined option that would give a host-specific directory name or filesystem to use by the diskless host to obtain host-specific applications and configuration data.

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Feb 19, 2011

Situation is a cable modem and a Belkin F5D8235 Wireless-N router (and a computer) are at one end of the property. Approx 150-200 ft away I want to put 3 desktop computers none of which have a wireless card or device. I DO have a Linksys WRT54G I'm not using.I want to hardwire the 3 desktop computers to a switch that is hard wired to the Linksys. Putting a wireless card in one of the 3 computers is not practical because of physical obstructions (a lot of cabinetry, furniture, walls) that the Linksys (which can be at the window) would not have to deal with.

Is it possible for the Linksys to 'receive' the wireless signal from the Belkin so the 3 desktops can share the internet? If not, what could I put in the window to 'receive' or 'repeat' the wireless signal?I know this isn't exactly a Ubuntu question, except that 2 of the 3 computers are 64bit Lucid.

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My email server sends mail but does not receive I can send mail using a mail server I have at home, I have a domain name I got at www.dyndns.com, but when I send mails to it they wont get delivered. Is it because I dont have the MX record?

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