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  • Cancel UDP recvfrom in C on Unix

    - by hora
    I'm just starting to learn how network programming in C works, and I've written a small program that sends messages to and from a UNIX terminal. I'm using pthreads in my program, one of which essentially just waits on recvfrom() to receive a message. However, I want to be able to close all threads properly if the users chooses to quit the program. The way I have it set up right now, a different thread just cancels the thread waiting on recvfrom, but I'm worried this might not be a good idea since I'm leaving sockets unclosed and I'm not freeing all the memory I allocated. Is there a way to cancel a recvfrom() call, or some way to run a certain routine upon cancelling a pthread? Thanks.

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  • Java: Multithreading & UDP Socket Programming

    - by Ravi
    I am new to multithreading & socket programming in Java. I would like to know what is the best way to implement 2 threads - one for receiving a socket and one for sending a socket. If what I am trying to do sounds absurd, pls let me know why! The code is largely inspired from Sun's tutorials online.I want to use Multicast sockets so that I can work with a multicast group. class server extends Thread { static protected MulticastSocket socket = null; protected BufferedReader in = null; public InetAddress group; private static class receive implements Runnable { public void run() { try { byte[] buf = new byte[256]; DatagramPacket pkt = new DatagramPacket(buf,buf.length); socket.receive(pkt); String received = new String(pkt.getData(),0,pkt.getLength()); System.out.println("From server@" + received); Thread.sleep(1000); } catch (IOException e) { System.out.println("Error:"+e); } catch (InterruptedException e) { System.out.println("Error:"+e); } } } public server() throws IOException { super("server"); socket = new MulticastSocket(4446); group = InetAddress.getByName("239.231.12.3"); socket.joinGroup(group); } public void run() { while(1>0) { try { byte[] buf = new byte[256]; DatagramPacket pkt = new DatagramPacket(buf,buf.length); //String msg = reader.readLine(); String pid = ManagementFactory.getRuntimeMXBean().getName(); buf = pid.getBytes(); pkt = new DatagramPacket(buf,buf.length,group,4446); socket.send(pkt); Thread t = new Thread(new receive()); t.start(); while(t.isAlive()) { t.join(1000); } sleep(1); } catch (IOException e) { System.out.println("Error:"+e); } catch (InterruptedException e) { System.out.println("Error:"+e); } } //socket.close(); } public static void main(String[] args) throws IOException { new server().start(); //System.out.println("Hello"); } }

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  • NFS Mounts Issues

    - by user554005
    Having some issue with a NFS Setup on the clients it just times out refuses to connect [root@host9 ~]# mount 192.168.0.17:/home/export /mnt/export mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). Here are the settings I'm using: [root@host17 /home/export]# cat /etc/hosts.allow # # hosts.allow This file contains access rules which are used to # allow or deny connections to network services that # either use the tcp_wrappers library or that have been # started through a tcp_wrappers-enabled xinetd. # # See 'man 5 hosts_options' and 'man 5 hosts_access' # for information on rule syntax. # See 'man tcpd' for information on tcp_wrappers # portmap: 192.168.0.0/255.255.255.0 lockd: 192.168.0.0/255.255.255.0 rquotad: 192.168.0.0/255.255.255.0 mountd: 192.168.0.0/255.255.255.0 statd: 192.168.0.0/255.255.255.0 [root@host17 /home/export]# cat /etc/hosts.deny # # hosts.deny This file contains access rules which are used to # deny connections to network services that either use # the tcp_wrappers library or that have been # started through a tcp_wrappers-enabled xinetd. # # The rules in this file can also be set up in # /etc/hosts.allow with a 'deny' option instead. # # See 'man 5 hosts_options' and 'man 5 hosts_access' # for information on rule syntax. # See 'man tcpd' for information on tcp_wrappers # portmap:ALL lockd:ALL mountd:ALL rquotad:ALL statd:ALL [root@host17 /home/export]# cat /etc/exports /home/export 192.168.0.0/255.255.255.0(rw) [root@host17 /home/export]# iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain RH-Firewall-1-INPUT (2 references) target prot opt source destination ACCEPT all -- anywhere anywhere ACCEPT icmp -- anywhere anywhere icmp any ACCEPT esp -- anywhere anywhere ACCEPT ah -- anywhere anywhere ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns ACCEPT udp -- anywhere anywhere udp dpt:ipp ACCEPT tcp -- anywhere anywhere tcp dpt:ipp ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:6379 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:sunrpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:sunrpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:nfs ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:32803 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:filenet-rpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:892 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:892 ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:rquotad ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:rquotad ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:pftp ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:pftp REJECT all -- anywhere anywhere reject-with icmp-host-prohibited on the clients here is some rpcinfos [root@host9 ~]# rpcinfo -p 192.168.0.17 program vers proto port 100000 4 tcp 111 portmapper 100000 3 tcp 111 portmapper 100000 2 tcp 111 portmapper 100000 4 udp 111 portmapper 100000 3 udp 111 portmapper 100000 2 udp 111 portmapper 100011 1 udp 875 rquotad 100011 2 udp 875 rquotad 100011 1 tcp 875 rquotad 100011 2 tcp 875 rquotad 100005 1 udp 45857 mountd 100005 1 tcp 55772 mountd 100005 2 udp 34021 mountd 100005 2 tcp 59542 mountd 100005 3 udp 60930 mountd 100005 3 tcp 53086 mountd 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100227 2 udp 2049 nfs_acl 100227 3 udp 2049 nfs_acl 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100227 2 tcp 2049 nfs_acl 100227 3 tcp 2049 nfs_acl 100021 1 udp 59832 nlockmgr 100021 3 udp 59832 nlockmgr 100021 4 udp 59832 nlockmgr 100021 1 tcp 36140 nlockmgr 100021 3 tcp 36140 nlockmgr 100021 4 tcp 36140 nlockmgr 100024 1 udp 46494 status 100024 1 tcp 49672 status [root@host9 ~]# [root@host9 ~]# rpcinfo -u 192.168.0.17 nfs rpcinfo: RPC: Timed out program 100003 version 0 is not available [root@host9 ~]# rpcinfo -u 192.168.0.17 portmap program 100000 version 2 ready and waiting program 100000 version 3 ready and waiting program 100000 version 4 ready and waiting [root@host9 ~]# rpcinfo -u 192.168.0.17 mount rpcinfo: RPC: Timed out program 100005 version 0 is not available [root@host9 ~]# I'm running CentOS 5.8 on all systems

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  • UDP server doesnt accept calls from outside.

    - by rayman
    Hi, ive implement simple udp server on my Android device.(sdk 1.5) it works fine when i am runnning a local client on the phone sends through it trigger to my server. but when i try to get udp call from an outside server to my phone, it doesnt work. already make sure the outside server isnt blocked by firewall and it's sending the udp trigger to the right port, which my phone is listening to. i used natstat on the phone and checked that the phone is realy listening to the it's local ip and the port ive setted it to. here is my code of the server:(on the device) // server will listen to one client try { Thread udpServerThread = new Thread() { @Override public void run() { try { // Retrieve the ServerName InetAddress serverAddr = InetAddress .getByName("localhost"); Log.d("UDP", "S: Connecting..."); // Create new UDP-Socket socket = new DatagramSocket(SERVERPORT,serverAddr); byte[] buf = new byte[17]; // * Prepare a UDP-Packet that can contain the data we // * want to receive DatagramPacket packet = new DatagramPacket(buf, buf.length); Log.d("UDP", "S: Receiving..."); // wait to Receive the UDP-Packet socket.receive(packet); Log.d("UDP", "S: Received: '" + new String(packet.getData()) + "'"); acceptedMsg=new String(packet.getData()); notifyService(acceptedMsg); Log.d("UDP", "S: Done."); } catch (Exception e) { Log.e("UDP", "S: Error", e); } } }; udpServerThread.start(); } catch (Exception E) { Log.e("r",E.getMessage()) ; } so as i said, when i try it with local client(seperate thread) which sends udp trigger it works fine, but when i take this client implementation and put it on an outside real server, after UDP being sent, the phone doesnt respond to it. any idea? thanks, ray.

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  • How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

    - by nikku
    I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 bytes, which means the packet size was 65507 + 20 (IP Header) + 8 (UDP Header) = 65535. If the frame's payload size itself is maximum of 1472 bytes (as per my textbook), how can the packet size of IP be greater than that which here is 65535? I used sender code as char buffer[100000]; for (int i = 1; i < 100000; i++) { int len = send (socket_id, buffer, i); printf("%d\n", len); } Receiver code as while (len = recv (socket_id, buffer, 100000)) { printf("%d\n". len); } I observed that send returns -1 on i > 65507 and recv prints or receives a packet of maximum of length 65507.

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  • How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

    - by nikku
    I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 bytes, which means the packet size was 65507 + 20 (IP Header) + 8 (UDP Header) = 65535. If the frame's payload size itself is maximum of 1472 bytes (as per my textbook), how can the packet size of IP be greater than that which here is 65535? I used sender code as char buffer[100000]; for (int i = 1; i < 100000; i++) { int len = send (socket_id, buffer, i); printf("%d\n", len); } Receiver code as while (len = recv (socket_id, buffer, 100000)) { printf("%d\n". len); } I observed that send returns -1 on i > 65507 and recv prints or receives a packet of maximum of length 65507.

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  • Can a network interface be configured to have a default gateway for UDP packets?

    - by Vaibhav
    It is quite possible that my question may not make a lot of sense. I apologize, but I am not a networking guy, and that's my excuse. To elaborate, WikiPedia defines "Default Gateway" as a node on a "TCP/IP" network. And the way it works is that if a network interface is sending a packet to an IP address not present on its subnet, it sends it out to the default gateway (which then knows what to do with that packet). Is this true if a UDP packet (datagram) is involved? I mean, if my network interface is sending a UDP packet to an IP address that is not present on its subnet, would it automatically send it to the Default Gateway as well?

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  • Google dévoile son nouveau protocole QUIC dans Chrome, qui combine le meilleur de TCP et UDP

    Google dévoile son nouveau protocole QUIC dans Chrome qui combine le meilleur de TCP et UDPAprès le protocole SPDY, permettant d'accélérer le Web en compressant les requêtes d'une page Web, Google expérimente un nouveau protocole qui offrira comme le précédent une vitesse de chargement des pages optimisée.Le géant de la recherche vient de dévoiler un premier aperçu du protocole expérimental Quick UDP Internet Connections (QUIC), dans la dernière version de son navigateur sur le canal Canary.QUIC a pour objectif de faire évoluer le protocole TCP en tirant parti des avantages qu'offre UDP. Le protocole repose sur un multiplexage de flux au dessus d'UDP, pour permettre des transmissions fiables en ...

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  • Does it make sense to have more than one UDP Datagram socket on standby? Are "simultaneous" packets

    - by Gubatron
    I'm coding a networking application on Android. I'm thinking of having a single UDP port and Datagram socket that receives all the datagrams that are sent to it and then have different processing queues for these messages. I'm doubting if I should have a second or third UDP socket on standby. Some messages will be very short (100bytes or so), but others will have to transfer files. My concern is, will the Android kernel drop the small messages if it's too busy handling the bigger ones? Update "The latter function calls sock_queue_rcv_skb() (in sock.h), which queues the UDP packet on the socket's receive buffer. If no more space is left on the buffer, the packet is discarded. Filtering also is performed by this function, which calls sk_filter() just like TCP did. Finally, data_ready() is called, and UDP packet reception is completed."

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  • UDP packets are dropped when its size is less than 12 byte in a certain PC. how do i figure it out the reason?

    - by waan
    Hi. i've stuck in a problem that is never heard about before. i'm making an online game which uses UDP packets in a certain character action. after i developed the udp module, it seems to work fine. though most of our team members have no problem, but a man, who is my boss, told me something is wrong for that module. i have investigated the problem, and finally i found the fact that... on his PC, if udp packet size is less than 12, the packet is never have been delivered to the other host. the following is some additional information: 1~11 bytes udp packets are dropped, 12 bytes and over 12 bytes packets are OK. O/S: Microsoft Windows Vista Business NIC: Attansic L1 Gigabit Ethernet 10/100/1000Base-T Controller WSASendTo returns TRUE. loopback udp packet works fine. how do you think of this problem? and what do you think... what causes this problem? what should i do for the next step for the cause? PS. i don't want to padding which makes length of all the packets up to 12 bytes.

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  • Continuous outbound connection from QNAP NAS

    - by user192702
    I notice on my firewall that my QNAP NAS is continuously sending UDP sessions out to the Internet. Every second I have 5 - 7 connections out to addresses like the following: 2013-11-10 23:17:54 Deny 192.168.60.5 93.215.212.162 6881/udp 6881 6881 2013-11-10 23:18:05 Deny 192.168.60.5 87.76.0.83 29872/udp 6881 29872 2013-11-10 23:18:05 Deny 192.168.60.5 5.164.188.224 6881/udp 6881 6881 2013-11-10 23:18:05 Deny 192.168.60.5 80.61.45.206 6881/udp 6881 6881 2013-11-10 23:18:34 Deny 192.168.60.5 37.117.204.129 6881/udp 6881 6881 2013-11-10 23:18:34 Deny 192.168.60.5 71.67.101.30 51413/udp 6881 51413 2013-11-10 23:18:34 Deny 192.168.60.5 89.28.92.191 8621/udp 6881 8621 2013-11-10 23:18:34 Deny 192.168.60.5 94.244.157.85 28221/udp 6881 28221 2013-11-10 23:18:34 Deny 192.168.60.5 213.241.61.240 9089/udp 6881 9089 2013-11-10 23:18:45 Deny 192.168.60.5 88.163.28.100 52721/udp 6881 52721 2013-11-10 23:18:45 Deny 192.168.60.5 37.55.190.20 10027/udp 6881 10027 2013-11-10 23:18:45 Deny 192.168.60.5 62.72.188.146 14306/udp 6881 14306 2013-11-10 23:19:14 Deny 192.168.60.5 85.53.244.205 51413/udp 6881 51413 2013-11-10 23:19:14 Deny 192.168.60.5 67.163.18.215 52130/udp 6881 52130 2013-11-10 23:19:14 Deny 192.168.60.5 86.172.105.140 9089/udp 6881 9089 2013-11-10 23:19:14 Deny 192.168.60.5 99.28.56.121 52383/udp 6881 52383 2013-11-10 23:19:14 Deny 192.168.60.5 109.60.184.249 46217/udp 6881 46217 2013-11-10 23:19:25 Deny 192.168.60.5 121.107.144.174 21135/udp 6881 21135 2013-11-10 23:19:25 Deny 192.168.60.5 84.39.116.180 48446/udp 6881 48446 2013-11-10 23:19:25 Deny 192.168.60.5 183.238.254.62 openvpn/udp 6881 1194 ......... This is frightening as it seems like it's been hacked to send information out. Has anyone observed this behaviour from their QNAP NAS?

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  • u32 filter udp lenght 0 to 29

    - by Mark Ocok
    Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21668 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21669 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21670 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 Sep 30 18:20:02 30AA30 kernel: ** IN_UDP DROP ** IN=eth0 OUT= MAC=b8:ac:6f:99:8e:b2:a8:d0:e5:bf:71:81:08:00 SRC=66.225.232.169 DST=68.68.27.84 LEN=28 TOS=0x00 PREC=0x00 TTL=49 ID=21671 DF PROTO=UDP SPT=48153 DPT=16078 LEN=8 It's Spoofing attack dos, how to block Spoofing UDP lenght 0 to 29 using u32 Flooder target udp length udp 0 to 29

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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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  • What would cause different rates of packet loss between client and server in UDP?

    - by febreezey
    If I've implemented a reliable UDP file transfer protocol and I have a file that deliberately drops a percentage of packets when I transmit, why would it be more evident that transmission time increases as the packet loss percentage increases going from the client to server as opposed from the server to the client? Is this something that can be explained as a result of the protocol? Here are my numbers from two separate experiments. I kept the max packet size to 500 Bytes and the opposite direction packet loss to 5% with a 1 Megabyte file: Server to Client loss Percentage varied: 1 MB file, 500 b segments, client to server loss 5% 1% : 17253 ms 3% : 3388 ms 5% : 7252 ms 10% : 6229 ms 11% : 12346 ms 13% : 11282 ms 15% : 9252 ms 20% : 11266 ms Client to Server loss percentage varied 1 MB file, 500 b segments, server to client loss 5% 1%: 4227 ms 3%: 4334 ms 5%: 3308 ms 10%: 31350 ms 11%: 36398 ms 13%: 48436 ms 15%: 65475 ms 20%: 120515 ms You can clearly see an exponential increase in the client to server group

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  • Netcat UDP File Transfer Between Two Servers Times Out?

    - by Mark Bowytz
    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 possible. Testing in TCP mode went well and I was wondering how UDP might fare. On my receiving (client) end, I ran this: nc -u -l 11225 -v > myfile.out And then on the sending (server) end I ran the following: cat myfile.out | nc -u myserver.foo.zzz.com 11225 -v The file I'm testing with is 38 GB but the transfer seems to stop at around 15 GB (one time at 14.9, another at 15.6). I've tested by adding a "-w 5000" just in case it's timing out but no joy. Adding the -v doesn't show anything except acknowledging that the connection occurred. No errors. So - any suggestions as to why would the transfer cease?

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  • Getting a UDP socket program in Python to accept messages from a Syslog client?

    - by Elvar
    I'm trying to write a Syslog listener and so far so good on getting it to accept incoming messages through TCP but I also want UDP to function. This is the UDP server code I'm using, which works using a python client app. I also have another app which also works just using the python client app. # Server program # UDP VERSION from socket import * # Set the socket parameters host = "localhost" port = 514 buf = 1024 addr = (host,port) # Create socket and bind to address UDPSock = socket(AF_INET,SOCK_DGRAM) UDPSock.bind(addr) # Receive messages while 1: data,addr = UDPSock.recvfrom(buf) if not data: print "Client has exited!" break else: print "\nReceived message '", data,"'" # Close socket UDPSock.close() Using this code I can send to the server and have it display the code. # Client program from socket import * # Set the socket parameters host = "localhost" port = 514 buf = 1024 addr = (host,port) # Create socket UDPSock = socket(AF_INET,SOCK_DGRAM) def_msg = "===Enter message to send to server==="; print "\n",def_msg # Send messages while (1): data = raw_input('>> ') if not data: break else: if(UDPSock.sendto(data,addr)): print "Sending message '",data,"'....." # Close socket UDPSock.close() I have tried the Kiwi Syslog Message Generator and Snare to send syslog messages to the UDP server and nothing comes up. Could someone help me understand?

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  • Why are UDP messages from outside the network received but not delivered?

    - by Warren Pena
    I have an Ubuntu Server 10.04 application I've developed that receives messages over a UDP port. The ultimate purpose of this application is to receive messages sent from workers' 3G modems out in the field. If use netcat on either another ubuntu Server or my Vista laptop (both on the same LAN as my test machine) to send a message, the message arrives correctly and appears in my application. However, if I go out to my car and use its 3G modem to send a message from the same Vista laptop, it doesn't work. If I run tcpdump -A, I see the message arrive correctly, but it's never delivered to my application. Clearly, the OS is the one making the choice not to deliver the messages (else they wouldn't appear in tcpdump nor would my app receive them when coming from local machines). I have not installed any firewall software on this machine, nor am I aware of anything installed by default that would block the traffic. sudo iptables --list returns Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination I'm not too familiar with iptables, but it looks to me like that's telling it to not do anything. What could be going on that's preventing my messages from being delivered?

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  • can I read exactly one UDP packet off a socket?

    - by Brian Palmer
    Using UNIX socket APIs on Linux, is there any way to guarantee that I read one UDP packet, and only one UDP packet? I'm currently reading packets off a non-blocking socket using recvmsg, with a buffer size a little larger than the MTU of our internal network. This should ensure that I can always receive the full UDP packet, but I'm not sure I can guarantee that I'll never receive more than one packet per recvmsg call, if the packets are small. The recvmsg man pages reference the MSG_WAITALL option, which attempts to wait until the buffer is filled. We're not using this, so does that imply that recvmsg will always return after one datagram is read? Is there any way to guarantee this? Ideally I'd like a cross-UNIX solution, but if that doesn't exist is there something Linux specific?

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  • Why is UDP + a software reliable ordering system faster than TCP?

    - by Ricket
    Some games today use a network system that transmits messages over UDP, and ensures that the messages are reliable and ordered. For example, RakNet is a popular game network engine. It uses only UDP for its connections, and has a whole system to ensure that packets can be reliable and ordered if you so choose. My basic question is, what's up with that? Isn't TCP the same thing as ordered, reliable UDP? What makes it so much slower that people have to basically reinvent the wheel?

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  • Does it make sense to have more than one UDP Datagram socket on standby? Are simultaneous packets dr

    - by Gubatron
    I'm coding a networking application on Android. I'm thinking of having a single UDP port and Datagram socket that receives all the datagrams that are sent to it and then have different processing queues for these messages. I'm doubting if I should have a second or third UDP socket on standby. Some messages will be very short (100bytes or so), but others will have to transfer files. My concern is, will the Android kernel drop the small messages if it's too busy handling the bigger ones?

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  • Can I configure Apache ActiveMQ to use the STOMP protocol over UDP?

    - by Marc C
    I'm developing a STOMP binding for Ada, which is working fine utilizing TCP/IP as the transport between the client and an ActiveMQ server configured as a STOMP broker. I thought to support UDP as well (i.e. STOMP over UDP), however, the lack of pertinent information in the ActiveMQ documentation or in web searches suggests to me that this isn't possible, and perhaps it doesn't even make any sense :-) Confirmation one way or the other (and an ActiveMQ configuration excerpt if this is possible) would be appreciated.

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  • How can I access UDP ports using a web application on the client PC?

    - by Vaibhav
    One of the thing that current Windows application does is that it writes out information to a hardware device via a UDP message. We are considering porting the application to web-based. I checked Silverlight, and that doesn't allow UDP. We don't want to use ActiveX or Java Applets. What are the other options? Thanks. Update - does anyone know if I can use Flash to do this?

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