Networking :: Client Receiving UDP From Multiple Sources ?
May 14, 2009
I have to implement a client/server solution that pretty much does this:
1) Client broadcasts UDP packet;
2) client receives answer packet from multiple servers - it includes the TCP port to use next and a list of files;
3) user picks file from list;
4) client downloads from server via TCP.
I got the client to broadcast and the servers reply. However, i'm not yet getting the client to be able to receive multiple packets.
I'm very inclined and have tried to implement select, but most examples i find are for stream sockets. Once the fsSet shows a read event would i create a new socket or just use the main socket for recvfrom()ing? I assume i need at least two sockets. However i'm not sure if this will allow the client to actually receive simultaneously... so i'm kinda not wanting to guess that this implies fork and threads... Also, i assume the socket must be nonblocking (done), although i've read somewhere select would take care of this?
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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
2.6.18-164.20.1.el5
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Feb 17, 2011
There is a segmentation fault error while receiving http request side program. Following is the code:
Code:
#include<iostream>
#include <sys/types.h>
[code]...
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Mar 9, 2011
I am writing a TCP server in C, and the server listens to incoming client connections and accepts them. It then creates a thread to handle the client. The clients are expected to only receive data from my server and not send any data. So if I use a select() call with a recv(), I believe that the recv() will just block forever since there will not be any data coming from the client. If I use a non-blocking recv(), then this will just return a 0 which tells me nothing because the client is not expected to send any data. I am not sure if I have misunderstood some socket concepts, but I need a solution to detect when the client has disconnected so that I can close the socket and stop sending data to the client. As I understand it, simple ACKs etc are not captured by the recv(), and only data sent by the client will cause recv() to return a non-zero value, so I am not sure how to know when the client has disconnected.
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Apr 30, 2010
I need to ask about some method let me to subscribe to some one who make satellite sharing by some file and cable attached to the Receiver to let you receive the stream of codes that he send
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Nov 15, 2010
I have configured postfix to send/receive mail from/to for two domains we manage. [URL] and [URL] Most of the cases there is no issue sending out or receiving emails. However, a few users of domainY.com complained that their senders were not able to sent them email. after much investigation, we started thinking that the mailserver failed to send us email may the failing on doing a SMTP Banner issue.
Is there anyone who knows how to deal with this SMTP banner issue with multiple domain. We want different SMTP banner when doing EHLO on different server.
530 mail.domainX.com ESMTP MailEnable Service, Version: 1.981-- denied access at 11/16/10 10:51:21
530 mail.domainY.com ESMTP MailEnable Service, Version: 1.981-- denied access at 11/16/10 10:51:21
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Nov 24, 2010
How to login multiple client pc on the same network using via openvpn server from client side
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Jul 13, 2009
I have a webserver setup, where i need the server to have multiple eht:0 aliases in order to do some SSL-vhosting and other stuff.
The servers eh0 is set up in /etc/network/interfaces (its an Ubuntu)
And i have added the eth aliases with : ifconfig eth0:1 123.231.213.123 up command.
This works great, i can use the additional IP�s for the SSL-vhosts, and all is good.
My problem now is that while the server itself has 1 IP, (and approx 20 IP on alias interfaces) it uses random (i think) IPs when it is to connect to other servers. E.g the main problem is that if a Vhost on the server sends out an email, the server uses a wrong IP in the headers. Thus making it seem like the email is coming from another IP than then on the Vhost it�s currently residing.
Currently, when the server connects to its smarthost in order to deliver emails, It connects from the IP that is bound to the eth0:0 interface, and not the IP bound to eth0 which is desired.
The question now is how do I sort out the IP�s so that all connections the server makes as a client, will use the first (Eth0) IP ?
And all the extra IP-adresses will only be used as "server addresses" not to make client requests.
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Jan 19, 2011
If I have a icecast program broadcasting to the net, and I want ppl from around the world to connect to it and mix their own audio into the stream ,what do I do?
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Aug 25, 2010
i'm using optical s/pdif output, called "hda intel, ad198x digital (iec958 (s/pdif) digital audio output)" in phonon preferences. sounds works just fine -- except i can't use multiple audio sources simultaneously: for example amarok+videos is a no-no. only the first audio source plays, so i have to close amarok in order to listen to any flash videos. i had this problem already with opensuse 11.2, but couldn't figure it out (using 11.3 now).
i just recently got a hunch that it might have something to do with mixing and the s/pdif, and i tried using analog output ("hda intel (ad198x analog)"). lo and behold, it works! amarok+flash that isash still doesn't still consider this a major leap forward.however, i'd like to keep using my optical output.
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Apr 5, 2010
i need a mod with the option multiple alternate sources download.
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Apr 12, 2011
I have suspicious requests in my haproxy logs from multiple sources to the same target. I could deny them in /etc/hosts.deny, but there are too many to keep track of. Is there a way to deny all requests to a specific target either in haproxy or through iptables?
Here's an example of the request: Apr 12 15:11:37 127.0.0.1 haproxy[28672]: 41.105.42.150:27072 [12/Apr/2011:15:11:37.315] web_servers frontend_farm/######## 3/0/1/1/169 404 1073 - - --NI 3/3/2/1/0 0/0 "GET /images/comment_icon.gif HTTP/1.1"
I've commented out my amazon instance id for security purposes. The request is for comment_icon.gif which does not exist. All requests go to that. The source IPs are from different countries as well. Blocking a certain country won't work either. Basically, if there was a way to send all requests for comment_icon.gif to /dev/null or something it would work.
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Feb 1, 2011
I have been receiving 4.5 KiB/s to 7.0 KiB/s on average. This is with nothing connected actively using Wi-Fi (browser, download, etc.) Why is this? It is happening on Lucid x86. I have a 64bit machine, but unfortunately neither the 32bit or 64bit wireless works "out of the box" for me. My wireless card is Ralink RT3090PCIe. I have not found a package to support my card in Ubuntu 64bit (I prefer 64bit over 32bit.). For now there is this as a package for Ubuntu 32bit https://launchpad.net/~markus-tisoft/+archive/rt3090
Another thing, as of late (about a week) my wireless connection strength has diminished substantially was 95-97% now 73-85% This is unusual. Hopefully not any shady neighbors.
I am strongly considering deleting the Ubuntu partition, until a 64bit works "out of the box" for the wireless or at the very least only use this Ubuntu 32bit Lucid version with all network permantly disconnected. To be fair, I have tried quite a few other 64bit Linux distributions (Live CDs) and these others did not work wirelessly "out of the box" either.
I am by no means a Windows "fanboi".....but Windows 64bit does work for me "out of the box", as it should. So, I may have to go there (back to Win7), until I find a release of Ubuntu 64bit that has a wireless that works for me, without any errors/problems.
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Aug 17, 2010
I have set up a server using Suse, which I have done several times. This one is running 11.2 'Emerald'. It has 2 network cards. One is connected to a bt router with a static ip, and the other is for the internal network. The server is used as the gateway for the internet via masquerading. I have 2 issues, which I suspect are related. I can ssh to and from the server fine, but if I try to scp a file, it is fine sending to a remote machine, but stalls if I try the other way.
It also stalls if I try and send from the remote machine to this one. I have tried debug mode, but no 'error's occur, it just stalls.The internet connection is also very slow and sometimes stalls, so there may be a link.I am not new to linux, but this has me baffled. This server replaced a Suse 10.2 server with similar config, and that worked fine.The firewall allows ssh, so I don't think its that.
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May 18, 2010
I have recently set up nagios on a ubuntu server (9.10), and set it up to monitor all the servers, switches etc, following the quickstart guide provided on the nagios website.My problem is this:I have setup the nagios-plugins, and tried to set it up to monitor the network switches via SNMP but receive the following within the nagios web interface:SNMP problem - No data received from host I tried it from the command line, and got the exact same error.Is there some further configuration I need to do to be able to get this data?I've used up all my google-fu, and read over everyone else's problems on every forum I could find, but to no avail.
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Apr 11, 2010
I have a computer with two interfaces: a fixed connection (eth1) and a modem (ppp0). My goal is to receive UDP packets from both connections concurrently (using the recv() function). The problem is, that the received packets reach the application only when the default gateway is set to that interface's address. For example, if I set the default gw to be in the eth1 subnet, only packets from eth1 reach the application. Other packets are received in the interface (checked using tcpdump), but they seem to be blocked somewhere. The policy defined in iptables is "ACCEPT" for all incoming packets, with no rules at all. I would like to know how to overcome this problem, and anyway how is the default gateway related to incoming UDP?
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Apr 8, 2010
If I type
Code:
$ ping [URL]
or even
Code:
$ ping google.com
should I receive a reply?
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Mar 8, 2010
We have connected two systems with ethernet cables and have configured the two systems with ipv6 addresses. The IP of one system is 2001:0db8:0:f101::1 (let's say X::1) (This system runs OS Fedora 10) and the other is 2001:0db8:0:f101::2. (Let's say X::2) (This system runs OpenSuSE 10.3) We are able to ping from both systems to the other. We are able to ssh into the one with IP X::2 from the one with IP X::1, but not vice versa.
We have disabled iptables on both systems by using the following commands:
/etc/init.d/iptables save
/etc/init.d/iptables stop
on the fedora 10 system and
# iptables -X
# iptables -t nat -F
# iptables -t nat -X
# iptables -t mangle -F
# iptables -t mangle -X
# iptables -P INPUT ACCEPT
# iptables -P FORWARD ACCEPT
# iptables -P OUTPUT ACCEPT
on the openSuse system.
The error we get in trying to ssh from the openSuse system to the fedora system is:
ssh: connect to host 2001:0db8:0:f101::1 port 22: Connection refused
We're trying to write server and client code to send data from one system to the other using SOCK_DGRAM. The code works fine when we run both the client and server on the same system. However, we are not able to send data from one system to another when we use the IPv6 addresses to run the client and server programs.
The error we get is:
sendto(): Operation not permitted
The codes we are using for the server and client programs can be found here in beej's guide here : [URL]. We've only substituted the appropriate addresses in the right places... We've disabled the iptables...
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Jun 25, 2010
I would like to send a data using one thread and receive a data using other thread by using a same socket connection using USD sockets. The calls i am using for sending and receiving are send(), recv(). let me know is it possible to send and receive the data parallel (Full duplex communication)?
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Mar 9, 2010
I'm using openvpn-2.0.9 with gui-1.0.3 which is set up on windows xp machines(for server and clients) when i set up the server and one client it connects well and i can work without a problem. but when the second client connects it gets the same ip address of the client1, so that both clients can't work at once.
my server and client config files are as follows.
server-configuration file
client1-configuration file
client2-configuration file
I've tried by changing many settings such as server-bridge and all but couldn't find a solution for the problem.
By the way when connected server gets 10.8.0.1/30 and every clients get same ip as 10.8.0.6/30
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May 16, 2011
I've got the following problem: I just noticed that there were just very few notifications about updating the system (usually there are damn many of them in a week) So I opened the update manager and clicked on "refresh list". The following result popped up: p,li{white-space:pre-wrap;}E: Error http://ppa.launchpad.net natty/main/Sources Sources 404 Not Found First I thought, it would be just some kind of server problem, but it didn't stop. The next thing was to research the thread and I even found something. However, the solution suggested didn't work at all. (Things, which might have caused this: I installed the default software center |I'm using Kubuntu, but in this case that fact doesn't matter| and used it. To sum up:
- not able to update the system referring to the launchpad main sources for 11.04
- following error: E: Error http://ppa.launchpad.net natty/main/Sources Sources 404 Not Found It would be great if this was a common issue and I've been simply too stupid to find a proper solution. So you could just post the link.
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Jan 6, 2011
trying to create a "local network" by directly connecting an IBM Thinkpad with Debian Linux installed on it to an Alix computer running Voyager Linux. I'm following a "how to" I found to create a music server, hence the requirement. My issue is I can't get a static IP address to be configured on the Debian machine.I've trawled the net and have found the instructions about editing the /etc/network/interfaces and have tried to do this. First I tried to get DHCP working so I could connect the Debian machine to the net and this proved successful. I edited the interfaces file to look as follows:
# The loopback network interface
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
Then I tried adding a static IP address to the machine. As this is a network purely between two machines I made up the IP addres and used 192.168.0.1 and used a NetMask calculator to give me a NetMask of 255.255.255.254 (I told the calculator there would be 2 machines on the network). I then edited the interfaces file as follows:
# The loopback network interface
auto lo
iface lo inet loopback
[code]....
I re-booted the machine (ifdown eth0 followed by ifup eth0 keeps saying that eth0 hasn't been configured - a problem there that I don't understand), but during boot up time it failed to assign the Static IP address to eth0 and made me go into SU mode. To fix it I simply replaced the interface file with the static IP inputs with the file that had the DHCP entries (I'd made a copy of the DHCP file), and re-started the machine. Everthing came up fine. So the first question is how do I get a static IP address to be assigned to eth0 such that whenever I shut down and restart the machine the static IP address is always loaded?
The second question is around creating the network via the cross over cable. From what I've found via Google, all I should have to do is create a static IP address on the Debian machine and a static IP address on the Voyager machine. Once they're connected by the cross over cable they should see each other. Is that correct, or do I have to do anything else?
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Apr 21, 2010
I am running Jolicloud on my netbook (which I believe is an Ubuntu derivative) and I am tried to enter the getdeb.net sources in so I can install apps from the website through APT but
1) When I entered the sources into sources.list and then the key into Terminal and then went to the site and tried to install an app it didn't work.
2) I deleted the line of code in the sources.list file and when I opened terminal and entered "sudo apt-get update" it showed the list of sources, but on the list were Getdeb.net sources.
My question is how do I delete sources that aren't in /etc/apt/sources.list ?
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Mar 30, 2011
I have a linux box with two interfaces: eth0 is a builtin and eth1 is a USB-LAN.
There is an IP configured on eth1.
eth0 is up but no IP is configured. This interface is used for sniffing with tcpdump.
The problem is that eth0 frequently stops receiving packets -- my tcpdump captures are empty, and if I look at the interface stats with ifconfig, I can see that no packets are received.
If I bounce the interface (ifconfig eth0 down; ifconfig eth0 up), it starts receiving packets again.
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May 19, 2010
I have a server which is used by number of client Apps. Now when a client initiates a sendto request to a server it has to respond(after recvfrom) by sending a message using sendto back to client and this should be done back and forth.
What I dont understand is, does the client have to open a new port to receive packets from client? If yes, then how will server know to what port of the client(assuming server ports are well-known to clients)?
I had given up on sending messages back and forth using UDP and switched to TCP. I could send a read and write message back and forth. But the trouble comes when I have more than one client wanting to talk to server using SOCK_STREAM. The first one gets through but the second client seems to get blocked forever(but I got no error upon socket creation or upon connect with the server on the same port as the previous client)..
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Nov 30, 2010
I have written a server application which has select for both incoming new client connection requests and incoming data from client. I am able to process incoming connection requests and client data.
For example, server has 8 clients connected to it. If client 3 disconnects from server, how will server come to know this client has disconnected and to close its client socket fd gracefully? Does server's select get data on that client socket fd as 'close' data or any error code in recv() function that notifies server to close this client socket fd? Also if client disconnects abruptly without sending close request to server, how should server handle this? Does server get "EPIPE" error?
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Jul 1, 2010
I am new in client server programming and i have written code for single server to single client communicating one port(3490). but i have no idea how my single server will be communicate with different client on different port.how this will be happen ?
Any idea to understand the logic or send any good link or any piece of code in c , i searched on net but all help was mostly for java progamming.
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Nov 23, 2010
I am looking for a PHP based IMPA client with these requirements:
- User accounts (not same as imap email accounts)
- Each user can add multiple IMAP emails to his account and check/use them.
Is there any solution for my requirements. I checked Squirrelmail and roundcube but I am not sure they can do this.
Otherwise I will need to either develop a system from scratch or modify an existing one to do my job. I hesitate to develop myself as it will take months if not years to make it stable and bug free.
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Nov 7, 2010
I still try update my broadcom drivers, because when I try use airodump-ng i receive error.
This error:
Interface Chipset Driver
eth1 Unknown wl (monitor mode enabled)[code]....
I dont know why receive this error WARNING: modpost: missing MODULE_LICENSE() in /home/mobile/Desktop/wdriver/wl.o
see include/linux/module.h for more information
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Aug 28, 2009
I am installing a hp officejet pro 8500 all in one printer to knoppix 6.0.1. install hangs saying i need to disable cd sources in etc/apt/source.list. How do i do this?
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