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  • iptables change destination address base on result from mysql

    - by user1812225
    I need to change destination address of tcp/ip packets based on result of execution mysql query... SELECT `score` FROM `reputation` WHERE `ip` = packet.source_ip if (score < a) then packet.destination_ip = ... else packet.destination_ip = ... What ways of solving this problem do you see? Thanks. P.S. this is important that destination host knows REAL ip address where packet came from, not IP address of firewall.

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  • Creating a Reverse Proxy using Jpcap

    - by Ramon Marco Navarro
    I need to create a program that receives HTTP request and forwards those requests to the web servers. I have successfully made this using only Java Sockets but the client needed the program to be implemented in Jpcap. I'd like to know if this is possible and what literature I should be reading for this project. This is what I have now by stitching together pieces from the Jpcap tutorial: import java.net.InetAddress; import java.io.*; import jpcap.*; import jpcap.packet.*; public class Router { public static void main(String args[]) { //Obtain the list of network interfaces NetworkInterface[] devices = JpcapCaptor.getDeviceList(); //for each network interface for (int i = 0; i < devices.length; i++) { //print out its name and description System.out.println(i+": "+devices[i].name + "(" + devices[i].description+")"); //print out its datalink name and description System.out.println(" datalink: "+devices[i].datalink_name + "(" + devices[i].datalink_description+")"); //print out its MAC address System.out.print(" MAC address:"); for (byte b : devices[i].mac_address) System.out.print(Integer.toHexString(b&0xff) + ":"); System.out.println(); //print out its IP address, subnet mask and broadcast address for (NetworkInterfaceAddress a : devices[i].addresses) System.out.println(" address:"+a.address + " " + a.subnet + " "+ a.broadcast); } int index = 1; // set index of the interface that you want to open. //Open an interface with openDevice(NetworkInterface intrface, int snaplen, boolean promics, int to_ms) JpcapCaptor captor = null; try { captor = JpcapCaptor.openDevice(devices[index], 65535, false, 20); captor.setFilter("port 80 and host 192.168.56.1", true); } catch(java.io.IOException e) { System.err.println(e); } //call processPacket() to let Jpcap call PacketPrinter.receivePacket() for every packet capture. captor.loopPacket(-1,new PacketPrinter()); captor.close(); } } class PacketPrinter implements PacketReceiver { //this method is called every time Jpcap captures a packet public void receivePacket(Packet p) { JpcapSender sender = null; try { NetworkInterface[] devices = JpcapCaptor.getDeviceList(); sender = JpcapSender.openDevice(devices[1]); } catch(IOException e) { System.err.println(e); } IPPacket packet = (IPPacket)p; try { // IP Address of machine sending HTTP requests (the client) // It's still on the same LAN as the servers for testing purposes. packet.dst_ip = InetAddress.getByName("192.168.56.2"); } catch(java.net.UnknownHostException e) { System.err.println(e); } //create an Ethernet packet (frame) EthernetPacket ether=new EthernetPacket(); //set frame type as IP ether.frametype=EthernetPacket.ETHERTYPE_IP; //set source and destination MAC addresses // MAC Address of machine running reverse proxy server ether.src_mac = new MacAddress("08:00:27:00:9C:80").getAddress(); // MAC Address of machine running web server ether.dst_mac = new MacAddress("08:00:27:C7:D2:4C").getAddress(); //set the datalink frame of the packet as ether packet.datalink=ether; //send the packet sender.sendPacket(packet); sender.close(); //just print out a captured packet System.out.println(packet); } } Any help would be greatly appreciated. Thank you.

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  • How broken is routing strategy that causes a martian packet (so far only) during tracepath?

    - by lkraav
    I believe I've achieved a table that routes packets from and to eth1/192.168.3.x through 192.168.3.1, and packets from and to eth0/192.168.1.x through 192.168.1.1 (helpful source). Question: when doing tracepath from 192.168.3.20 (from within vserver), I'm getting kernel: [318535.927489] martian source 192.168.3.20 from 212.47.223.33, on dev eth0 at or near the target IP, while intermediary hops go without (log below). I don't understand why this packet is arriving on eth0, instead of eth1, even after reading this: Note that you may see packets from non-routable IP addresses when running the traceroute or tracepath commands. While packets cannot be routed to these routers, packets sent between 2 routers only need to know the address of the next hop within the local networks, which could be a non-routable address. Can someone explain that paragraph in human language? Based on short initial trials so far, everything else seems to work without causing martians. Is this contained to the nature of tracepath operation or do I have some other bigger routing problem that will cause work traffic breakage? Side note: is it possible to inspect martian packet with tcpdump or wireshark or anything of the sort? I'm have not been able to get it to show up on my own. vserver-20 / # tracepath -n 212.47.223.33 1: 192.168.3.2 0.064ms pmtu 1500 1: 192.168.3.1 1.076ms 1: 192.168.3.1 1.259ms 2: 90.191.8.2 1.908ms 3: 90.190.134.194 2.595ms 4: 194.126.123.94 2.136ms asymm 5 5: 195.250.170.22 2.266ms asymm 6 6: 212.47.201.86 2.390ms asymm 7 7: no reply 8: no reply 9: no reply ^C Host routing: $ sudo ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo 2: sit0: <NOARP> mtu 1480 qdisc noop state DOWN link/sit 0.0.0.0 brd 0.0.0.0 3: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:24:1d:de:b3:5d brd ff:ff:ff:ff:ff:ff inet 192.168.1.2/24 scope global eth0 4: eth1: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:46:46:a3:6a brd ff:ff:ff:ff:ff:ff inet 192.168.3.2/27 scope global eth1 inet 192.168.3.20/27 brd 192.168.3.31 scope global secondary eth1 # linux-vserver instance $ sudo ip route default via 192.168.1.1 dev eth0 metric 3 unreachable 127.0.0.0/8 scope host 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.2 192.168.3.0/27 dev eth1 proto kernel scope link src 192.168.3.2 $ sudo ip rule 0: from all lookup local 32764: from all to 192.168.3.0/27 lookup dmz 32765: from 192.168.3.0/27 lookup dmz 32766: from all lookup main 32767: from all lookup default $ sudo ip route show table dmz default via 192.168.3.1 dev eth1 metric 4 192.168.3.0/27 dev eth1 scope link metric 4 Gateway routing # ip route 10.24.0.2 dev tun0 proto kernel scope link src 10.24.0.1 10.24.0.0/24 via 10.24.0.2 dev tun0 192.168.3.0/24 dev br-dmz proto kernel scope link src 192.168.3.1 192.168.1.0/24 dev br-lan proto kernel scope link src 192.168.1.1 $ISP_NET/23 dev eth0.1 proto kernel scope link src $WAN_IP default via $ISP_GW dev eth0.1 Additional background Options for non-virtualized network interface isolation?

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  • How to implement RFC 3393 (Ipdv packet delay varation) in C?

    - by sagar
    Hello , I am building an Ethernet Application in which i will be sending packets from one side and receiving it on the other side. I want to calculate delay in packets at the receiver side as in RFC 3393. So I have to put a timestamps in the packet at the sender side and then take the timestamps at the receiver side as soon as i receive the packet . Subtracting the values i will get the difference in timestamps and then subtracting this value with subsequent difference i will get One way ipdv delay . Both the clocks are not synchronized . So any help is greatly appreciated. Thank you.

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  • Mac OS X L2TP VPN won't connect

    - by smokris
    I'm running Mac OS X Server 10.6, providing an L2TP VPN service. The VPN works just fine when connecting from all computers except one --- this one computer stays at the "Connecting..." stage for a while, then says "The L2TP-VPN server did not respond". In the console, I see this: 6/7/10 10:48:07 AM pppd[341] pppd 2.4.2 (Apple version 412.0.10) started by jdoe, uid 503 6/7/10 10:48:07 AM pppd[341] L2TP connecting to server 'foo.bar.baz.edu' (256.256.256.256)... 6/7/10 10:48:07 AM pppd[341] IPSec connection started 6/7/10 10:48:07 AM racoon[342] Connecting. 6/7/10 10:48:07 AM racoon[342] IKE Packet: transmit success. (Initiator, Main-Mode message 1). 6/7/10 10:48:08 AM racoon[342] IKE Packet: receive success. (Initiator, Main-Mode message 2). 6/7/10 10:48:08 AM racoon[342] IKE Packet: transmit success. (Initiator, Main-Mode message 3). 6/7/10 10:48:08 AM racoon[342] IKE Packet: receive success. (Initiator, Main-Mode message 4). 6/7/10 10:48:08 AM racoon[342] IKE Packet: transmit success. (Initiator, Main-Mode message 5). 6/7/10 10:48:11 AM racoon[342] IKE Packet: transmit success. (Phase1 Retransmit). 6/7/10 10:48:14 AM racoon[342] IKE Packet: transmit success. (Phase1 Retransmit). 6/7/10 10:48:17 AM racoon[342] IKE Packet: transmit success. (Phase1 Retransmit). ...and the "retransmit" messages continue until the error message pops up. So far I've unsuccessfully tried: rebooting deleting the VPN profile and recreating it verifying the client's internet connection (it is able to reach the VPN server) connecting through several different networks (in case a router was blocking VPN packets) disabling the Mac OS X Firewall on the client making sure that the VPN settings exactly match those of other working computers running software update (the client is on 10.6.3) Any ideas?

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  • How can I reinstall QoS Packet Scheduler if it was removed from the winxp installation by nLite?

    - by Irwin1138
    I have a WinXP SP3 installation modified by nLite. This particular installation was stripped off the QoS Packet Scheduler. I was advised to remove QoS because of the overhead it produces or something like that. Now, I read this lifehacker post about windows maintenance, and it says that on the contrary, by doing so I may have done more harm than good: Disabling QoS in Windows XP: Rumor had it that Microsoft had permanently tied up 20 percent of your net bandwidth for Windows Update. They didn't, and those who disable QoS, or IPv6, in XP actually end up with some pretty harsh connectivity problems. I tend to believe this, and now I seek a way to reinstall QoS. I tried to install it by going to network adapter properties - install - service, but there is no QoS there. I have the original, untouched WinXP SP3 cd. So, is there a way to bring back QoS into my WinXP installation, preferably without reinstalling windows from scratch?

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  • l2tp / ipsec debian Openswan U2.6.38 does not connect

    - by locojay
    i am trying to get ipsec/l2tp running on a debian server with an iphone as a client but always get: Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [RFC 3947] method set to=115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike] meth=114, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-08] meth=113, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-07] meth=112, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-06] meth=111, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-05] meth=110, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-04] meth=109, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-03] meth=108, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-02] meth=107, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [draft-ietf-ipsec-nat-t-ike-02_n] meth=106, but already using method 115 Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: ignoring Vendor ID payload [FRAGMENTATION 80000000] Dec 2 21:00:04 vpn pluto[22711]: packet from <clientip>:43598: received Vendor ID payload [Dead Peer Detection] Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: responding to Main Mode from unknown peer <clientip> Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: transition from state STATE_MAIN_R0 to state STATE_MAIN_R1 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: STATE_MAIN_R1: sent MR1, expecting MI2 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: NAT-Traversal: Result using draft-ietf-ipsec-nat-t-ike (MacOS X): both are NATed Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: transition from state STATE_MAIN_R1 to state STATE_MAIN_R2 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: STATE_MAIN_R2: sent MR2, expecting MI3 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: ignoring informational payload, type IPSEC_INITIAL_CONTACT msgid=00000000 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: Main mode peer ID is ID_IPV4_ADDR: '10.2.210.176' Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[4] <clientip> #20: switched from "L2TP-PSK-noNAT" to "L2TP-PSK-noNAT" Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: deleting connection "L2TP-PSK-noNAT" instance with peer <clientip> {isakmp=#0/ipsec=#0} Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: transition from state STATE_MAIN_R2 to state STATE_MAIN_R3 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: new NAT mapping for #20, was <clientip>:43598, now <clientip>:49826 Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: STATE_MAIN_R3: sent MR3, ISAKMP SA established {auth=OAKLEY_PRESHARED_KEY cipher=aes_256 prf=oakley_sha group=modp1024} Dec 2 21:00:04 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: Dead Peer Detection (RFC 3706): enabled Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: the peer proposed: <public ip>/32:17/1701 -> 10.2.210.176/32:17/0 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: NAT-Traversal: received 2 NAT-OA. using first, ignoring others Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: responding to Quick Mode proposal {msgid:311d3282} Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: us: 171.138.2.13<171.138.2.13>:17/1701 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: them: <clientip>[10.2.210.176]:17/61719 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: transition from state STATE_QUICK_R0 to state STATE_QUICK_R1 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: STATE_QUICK_R1: sent QR1, inbound IPsec SA installed, expecting QI2 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: Dead Peer Detection (RFC 3706): enabled Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: transition from state STATE_QUICK_R1 to state STATE_QUICK_R2 Dec 2 21:00:05 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #21: STATE_QUICK_R2: IPsec SA established transport mode {ESP=>0x05e23c9a <0x216077a9 xfrm=AES_256-HMAC_SHA1 NATOA=10.2.210.176 NATD=<clientip>:49826 DPD=enabled} Dec 2 21:00:26 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: received Delete SA(0x05e23c9a) payload: deleting IPSEC State #21 Dec 2 21:00:26 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: received and ignored informational message Dec 2 21:00:27 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip> #20: received Delete SA payload: deleting ISAKMP State #20 Dec 2 21:00:27 vpn pluto[22711]: "L2TP-PSK-noNAT"[5] <clientip>: deleting connection "L2TP-PSK-noNAT" instance with peer <clientip> {isakmp=#0/ipsec=#0} Dec 2 21:00:27 vpn pluto[22711]: packet from <clientip>:49826: received and ignored informational message Dec 2 21:00:27 vpn pluto[22711]: ERROR: asynchronous network error report on eth0 (sport=4500) for message to <clientip> port 49826, complainant <clientip>: Connection refused [errno 111, origin ICMP type 3 code 3 (not authenticated)] my setup looks like this verizon fios actiontec -- DMZ-- ddwrt router -- debian xen instance actiontec : 192.168.1.1 ddwrt: 171.138.2.1 debian xen server: 171.138.2.13 forwarded udp 500, 4500, 1701 on ddwrt to debian xen instance. vpn passthrough is enabled /etc/ipsec.conf config setup dumpdir=/var/run/pluto/ nat_traversal=yes virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12,%v4:25.0.0.0/8,%v6:fd00::/8,%v6:fe80::/10,%v4:!171.138.2.0/24,%v4:!192.168.1.0/24 protostack=netkey # Add connections here conn L2TP-PSK-NAT rightsubnet=vhost:%priv also=L2TP-PSK-noNAT conn L2TP-PSK-noNAT authby=secret pfs=no auto=add keyingtries=3 # we cannot rekey for %any, let client rekey rekey=no # Apple iOS doesn't send delete notify so we need dead peer detection # to detect vanishing clients dpddelay=30 dpdtimeout=120 dpdaction=clear # Set ikelifetime and keylife to same defaults windows has ikelifetime=8h keylife=1h # l2tp-over-ipsec is transport mode type=transport # left=171.138.2.13 # # For updated Windows 2000/XP clients, # to support old clients as well, use leftprotoport=17/%any leftprotoport=17/1701 # # The remote user. # right=%any # Using the magic port of "%any" means "any one single port". This is # a work around required for Apple OSX clients that use a randomly # high port. rightprotoport=17/%any #force all to be nat'ed. because of ios conn passthrough-for-non-l2tp type=passthrough left=171.138.2.13 leftnexthop=171.138.2.1 right=0.0.0.0 rightsubnet=0.0.0.0/0 auto=route /etc/xl2tp/xl2tp.conf [global] ipsec saref = no listen-addr = 171.138.2.13 ;port = 1701 ;debug network = yes ;debug tunnel = yes ;debug network = yes ;debug packet = yes [lns default] ip range = 171.138.2.231-171.138.2.239 local ip = 171.138.2.13 assign ip = yes require chap = no refuse pap = no require authentication = no ;name = OpenswanVPN ppp debug = yes pppoptfile = /etc/ppp/options.xlt2tpd lenght bit = yes /etc/ppp/options.xl2tpd ;require-mschap-v2 pcp-accept-local ipcp-accept-local ipcp-accept-remote ;ms-dns 171.138.2.1 ms-dns 192.168.1.1 ms-dns 8.8.8.8 name l2tpd noccp auth crtscts idle 1800 mtu 1410 mru 1410 lock proxyarp connect-delay 5000 debug dump logfd 2 logfile /var/log/xl2tpd.log ipsec verify Checking your system to see if IPsec got installed and started correctly: Version check and ipsec on-path [OK] Linux Openswan U2.6.38/K3.0.0-1-amd64 (netkey) Checking for IPsec support in kernel [OK] SAref kernel support [N/A] NETKEY: Testing XFRM related proc values [OK] [OK] [OK] Checking that pluto is running [OK] Pluto listening for IKE on udp 500 [OK] Pluto listening for NAT-T on udp 4500 [OK] Two or more interfaces found, checking IP forwarding [FAILED] Checking NAT and MASQUERADEing [OK] Checking for 'ip' command [OK] Checking /bin/sh is not /bin/dash [WARNING] Checking for 'iptables' command [OK] Opportunistic Encryption Support [DISABLED] The failed can be ignored i guess since cat /proc/sys/net/ipv4/ip_forward returns 1 any help would be much appreciated as i don't have any idea why this is not working

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  • Movement prediction for non-shooters

    - by ShadowChaser
    I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction implementation in place. Physics/Movement The game doesn't have a true physics implementation, but uses the basic principles to implement movement. Rather than continually polling input, state changes (ie/ mouse down/up/move events) are used to change the state of the character entity the player is controlling. The player's direction (ie/ north-east) is combined with a constant speed and turned into a true 3D vector - the entity's velocity. In the main game loop, "Update" is called before "Draw". The update logic triggers a "physics update task" that tracks all entities with a non-zero velocity uses very basic integration to change the entities position. For example: entity.Position += entity.Velocity.Scale(ElapsedTime.Seconds) (where "Seconds" is a floating point value, but the same approach would work for millisecond integer values). The key point is that no interpolation is used for movement - the rudimentary physics engine has no concept of a "previous state" or "current state", only a position and velocity. State Change and Update Packets When the velocity of the character entity the player is controlling changes, a "move avatar" packet is sent to the server containing the entity's action type (stand, walk, run), direction (north-east), and current position. This is different from how 3D first person games work. In a 3D game the velocity (direction) can change frame to frame as the player moves around. Sending every state change would effectively transmit a packet per frame, which would be too expensive. Instead, 3D games seem to ignore state changes and send "state update" packets on a fixed interval - say, every 80-150ms. Since speed and direction updates occur much less frequently in my game, I can get away with sending every state change. Although all of the physics simulations occur at the same speed and are deterministic, latency is still an issue. For that reason, I send out routine position update packets (similar to a 3D game) but much less frequently - right now every 250ms, but I suspect with good prediction I can easily boost it towards 500ms. The biggest problem is that I've now deviated from the norm - all other documentation, guides, and samples online send routine updates and interpolate between the two states. It seems incompatible with my architecture, and I need to come up with a better movement prediction algorithm that is closer to a (very basic) "networked physics" architecture. The server then receives the packet and determines the players speed from it's movement type based on a script (Is the player able to run? Get the player's running speed). Once it has the speed, it combines it with the direction to get a vector - the entity's velocity. Some cheat detection and basic validation occurs, and the entity on the server side is updated with the current velocity, direction, and position. Basic throttling is also performed to prevent players from flooding the server with movement requests. After updating its own entity, the server broadcasts an "avatar position update" packet to all other players within range. The position update packet is used to update the client side physics simulations (world state) of the remote clients and perform prediction and lag compensation. Prediction and Lag Compensation As mentioned above, clients are authoritative for their own position. Except in cases of cheating or anomalies, the client's avatar will never be repositioned by the server. No extrapolation ("move now and correct later") is required for the client's avatar - what the player sees is correct. However, some sort of extrapolation or interpolation is required for all remote entities that are moving. Some sort of prediction and/or lag-compensation is clearly required within the client's local simulation / physics engine. Problems I've been struggling with various algorithms, and have a number of questions and problems: Should I be extrapolating, interpolating, or both? My "gut feeling" is that I should be using pure extrapolation based on velocity. State change is received by the client, client computes a "predicted" velocity that compensates for lag, and the regular physics system does the rest. However, it feels at odds to all other sample code and articles - they all seem to store a number of states and perform interpolation without a physics engine. When a packet arrives, I've tried interpolating the packet's position with the packet's velocity over a fixed time period (say, 200ms). I then take the difference between the interpolated position and the current "error" position to compute a new vector and place that on the entity instead of the velocity that was sent. However, the assumption is that another packet will arrive in that time interval, and it's incredibly difficult to "guess" when the next packet will arrive - especially since they don't all arrive on fixed intervals (ie/ state changes as well). Is the concept fundamentally flawed, or is it correct but needs some fixes / adjustments? What happens when a remote player stops? I can immediately stop the entity, but it will be positioned in the "wrong" spot until it moves again. If I estimate a vector or try to interpolate, I have an issue because I don't store the previous state - the physics engine has no way to say "you need to stop after you reach position X". It simply understands a velocity, nothing more complex. I'm reluctant to add the "packet movement state" information to the entities or physics engine, since it violates basic design principles and bleeds network code across the rest of the game engine. What should happen when entities collide? There are three scenarios - the controlling player collides locally, two entities collide on the server during a position update, or a remote entity update collides on the local client. In all cases I'm uncertain how to handle the collision - aside from cheating, both states are "correct" but at different time periods. In the case of a remote entity it doesn't make sense to draw it walking through a wall, so I perform collision detection on the local client and cause it to "stop". Based on point #2 above, I might compute a "corrected vector" that continually tries to move the entity "through the wall" which will never succeed - the remote avatar is stuck there until the error gets too high and it "snaps" into position. How do games work around this?

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  • Are there any concrete examples of where a paralellizing compiler would provide a value-adding benefit?

    - by jamie
    Paul Graham argues that: It would be great if a startup could give us something of the old Moore's Law back, by writing software that could make a large number of CPUs look to the developer like one very fast CPU. ... The most ambitious is to try to do it automatically: to write a compiler that will parallelize our code for us. There's a name for this compiler, the sufficiently smart compiler, and it is a byword for impossibility. But is it really impossible? Can someone provide a concrete example where a paralellizing compiler would solve a pain point? Web-apps don't appear to be a problem: just run a bunch of Node processes. Real-time raytracing isn't a problem: the programmers are writing multi-threaded, SIMD assembly language quite happily (indeed, some might complain if we make it easier!). The holy grail is to be able to accelerate any program, be it MySQL, Garage Band, or Quicken. I'm looking for a middle ground: is there a real-world problem that you have experienced where a "smart-enough" compiler would have provided a real benefit, i.e that someone would pay for? A good answer is one where there is a process where the computer runs at 100% CPU on a single core for a painful period of time. That time might be 10 seconds, if the task is meant to be quick. It might be 500ms if the task is meant to be interactive. It might be 10 hours. Please describe such a problem. Really, that's all I'm looking for: candidate areas for further investigation. (Hence, raytracing is off the list because all the low-hanging fruit have been feasted upon.) I am not interested in why it cannot be done. There are a million people willing to point to the sound reasons why it cannot be done. Such answers are not useful.

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  • What are some good examples of Powernap scripts and its use?

    - by shootingstars
    I would like to use powernap for putting my media server into suspend mode, and I haven't been able to find any example /etc/powernap/action scripts out there, except these: one two three Does anybody have a good script or recommend particular techniques with its use? From the comments of the default /etc/powernap/action script: # You may do one of: # 1) Write your own custom script below and make this file executable, # calling some specific action, such as: # /usr/sbin/pm-suspend # /usr/sbin/pm-hibernate # /sbin/poweroff # echo 'I am wasting electricity' | mail [email protected] # 2) Replace this file with an executable script or binary # 3) Symlink this file to some other executable script or binary

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  • Are there any good examples of open source C# projects with a large number of refactorings?

    - by Arjen Kruithof
    I'm doing research into software evolution and C#/.NET, specifically on identifying refactorings from changesets, so I'm looking for a suitable (XP-like) project that may serve as a test subject for extracting refactorings from version control history. Which open source C# projects have undergone large (number of) refactorings? Criteria A suitable project has its change history publicly available, has compilable code at most commits and at least several refactorings applied in the past. It does not have to be well-known, and the code quality or number of bugs is irrelevant. Preferably the code is in a Git or SVN repository. The result of this research will be a tool that automatically creates informative, concise comments for a changeset. This should improve on the common development practice of just not leaving any comments at all. EDIT: As Peter argues, ideally all commit comments would be teleological (goal-oriented). Practically, if a comment is made at all it is often descriptive, merely a summary of the changes. Sadly we're a long way from automatically inferring developer intentions!

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  • Any ideas why Ettercap filters aren't seeing packet data?

    - by Bryan
    I'm using an Ettercap filter to detect a query response coming back from a particular service on a remote machine. When I see a response from the service, I'm searching through the data in the packet to see if an offset is a specific value, and if so I'm changing the value at another offset. Trouble is, when I try this on a new virtual machine I built my Ettercap filter's no longer getting any data in the DATA.data variable available to it. if(ip.proto == TCP && tcp.src == 17867) { msg("Response seen!\n"); if(DATA.data + 2 == "\0x01") { msg("Flag detected!\n"); DATA.data + 5 = 0x09; } } The filter's getting applied to the traffic because "Response seen!" messages get printed out by Ettercap. However, "Flag detected!" messages do not. I think DATA.data is indeed empty because if I change my second "if" statement to check for DATA.data == "" then the "Flag detected!" message gets printed. Any ideas why this may be happening?! Also, if this is the wrong site to be asking questions like this, please let me know. I wasn't sure if it fit better here or somewhere like superuser or serverfault. By the way, this is a cross-post from StackOverflow... I should have posted on this forum instead I think. :)

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  • Are there any actual examples of profitable programmer's "worker's cooperatives"?

    - by Wannabe Tycoon
    http://en.wikipedia.org/wiki/Worker_cooperative I'm curious whether there are, anywhere in the world, worker's cooperatives that center on a technology business that involves either programming, IT, or some sort of IT or programming related consulting or services. The wikipedia link above is an overview of the concept. The short form explanation is that a co-op is a worker-owned business. Also there is the notion that every worker owns shares in the business. I am interested in knowing whether an example of a "programmer's/IT co-op" even exists. Note: I am not talking about nor asking about a government-funded incubator nor any other socialized, state supported group. I also don't mean "co-working", which is renting an office with other self employed people doing their own thing. I mean a going, profitable IT business operating in a competitive environment that is worker-owned and run.

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  • Can I make a "TCP packet modifier" using tun/tap and raw sockets?

    - by benhoyt
    I have a Linux application that talks TCP, and to help with analysis and statistics, I'd like to modify the data in some of the TCP packets that it sends out. I'd prefer to do this without hacking the Linux TCP stack. The idea I have so far is to make a bridge which acts as a "TCP packet modifier". My idea is to connect to the application via a tun/tap device on one side of the bridge, and to the network card via raw sockets on the other side of the bridge. My concern is that when you open a raw socket it still sends packets up to Linux's TCP stack, and so I couldn't modify them and send them on even if I wanted to. Is this correct? A pseudo-C-code sketch of the bridge looks like: tap_fd = open_tap_device("/dev/net/tun"); raw_fd = open_raw_socket(); for (;;) { select(fds = [tap_fd, raw_fd]); if (FD_ISSET(tap_fd, &fds)) { read_packet(tap_fd); modify_packet_if_needed(); write_packet(raw_fd); } if (FD_ISSET(raw_fd, &fds)) { read_packet(raw_fd); modify_packet_if_needed(); write_packet(tap_fd); } } Does this look possible, or are there other better ways of achieving the same thing? (TCP packet bridging and modification.)

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  • How do I get uri of HTTP packet with winpcap?

    - by Gtker
    Based on this article I can get all incoming packets. /* Callback function invoked by libpcap for every incoming packet */ void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data) { struct tm *ltime; char timestr[16]; ip_header *ih; udp_header *uh; u_int ip_len; u_short sport,dport; time_t local_tv_sec; /* convert the timestamp to readable format */ local_tv_sec = header->ts.tv_sec; ltime=localtime(&local_tv_sec); strftime( timestr, sizeof timestr, "%H:%M:%S", ltime); /* print timestamp and length of the packet */ printf("%s.%.6d len:%d ", timestr, header->ts.tv_usec, header->len); /* retireve the position of the ip header */ ih = (ip_header *) (pkt_data + 14); //length of ethernet header /* retireve the position of the udp header */ ip_len = (ih->ver_ihl & 0xf) * 4; uh = (udp_header *) ((u_char*)ih + ip_len); /* convert from network byte order to host byte order */ sport = ntohs( uh->sport ); dport = ntohs( uh->dport ); /* print ip addresses and udp ports */ printf("%d.%d.%d.%d.%d -> %d.%d.%d.%d.%d\n", ih->saddr.byte1, ih->saddr.byte2, ih->saddr.byte3, ih->saddr.byte4, sport, ih->daddr.byte1, ih->daddr.byte2, ih->daddr.byte3, ih->daddr.byte4, dport); } But how do I extract URI information in packet_handler?

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  • Where does "foo" come from in coding examples? [closed]

    - by ThePower
    Possible Duplicates: Using “Foo” and “Bar” in examples To foo bar, or not to foo bar: that is the question. Possible Duplicates: Using "Foo" and "Bar" in examples To foo bar, or not to foo bar: that is the question. Bit of a general question here, but it's something I would like to know! Whenever I am looking for resolutions to my C# problems online, I always come across "foo" being used as an example. Does this represent anything or is it just one of those unexplained catchy object names, used by many people in examples?

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  • Bridging and iptables SNAT conflict

    - by sad_admin
    Hello I am working on a setup here and have it working with one minor exception. Devices on one side of my bridge aren't getting SNAT'd to the Internet. The Diagram / Overview: Primary_Network (Site_A) | | Internet ------- Linux_Bridge_GW (GW) | | Secondary/CoLo Site (Site_B) Here is the setup: 1.) Site_A has all the production servers and workstations. 2.) Site_B has a set of servers that we would like to fail-over to and also serve our internet facing services from. 3.) GW has two interfaces that are trunked and carrying the appropriate VLAN traffic (allow layer-2 propagation of traffic between sites) //this all works perfectly fine. 4.) The problem that is being encountered is, hosts from Site_B have their default GW at Site_A (same subnet) GW does not have IPs on the VLANs that are being passed. 5.) All hosts at Site_A can reach the Internet without problem. 6.) GW has an addresses on a subnet that is ONLY for Internet destined traffic. (This was done so that Websense would not have to parse unnecessary traffic. We use this VLAN as the monitor port's source on the switch where Websense is sitting). What I think is happening: 1.) Packet/Frame comes in on physdev at Site_B destined for Internet. 2.) Kernel sees packet, and forwards it out the other side of the bridge to that host's default GW. 3.) Site_A (containing core-network's Default-GW) sees that packet is destined for a host it doesn't know about, so it sends it to it's default GW (the linux bridge, since it's Internet bound). 4.) The kernel says "Hey, I've seen you before" and therefore doesn't do SNAT'ing on the packet and sends it out to the Internet where it's black-holed. Why I think it's happening: 1.) A tcpdump on the internet facing NIC shows the packet leaving the interface with the private address as it's source. What I would like: 1.) Have the packet SNAT'd. 2.) Something like the below would be awesome a.) packet comes in from Site_B b.) kernel sees that the packet is NOT destined for itself or any private address c.) kernel says "OK, well since you're destined for the Internet I'm going to send you out this interface rather than forward you to your normal default GW that's WAAAY over there." d.) packet comes in from internet and is sent out the appropriate bridge physdev depending on which site the host it's destined for is at. Thanks for any assistance or guidance that you are willing to offer. Best Regards, Sad Admin

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  • Unnecessary Java context switches

    - by Paul Morrison
    I have a network of Java Threads (Flow-Based Programming) communicating via fixed-capacity channels - running under WindowsXP. What we expected, based on our experience with "green" threads (non-preemptive), would be that threads would switch context less often (thus reducing CPU time) if the channels were made bigger. However, we found that increasing channel size does not make any difference to the run time. What seems to be happening is that Java decides to switch threads even though channels aren't full or empty (i.e. even though a thread doesn't have to suspend), which costs CPU time for no apparent advantage. Also changing Thread priorities doesn't make any observable difference. My question is whether there is some way of persuading Java not to make unnecessary context switches, but hold off switching until it is really necessary to switch threads - is there some way of changing Java's dispatching logic? Or is it reacting to something I didn't pay attention to?! Or are there other asynchronism mechanisms, e.g. Thread factories, Runnable(s), maybe even daemons (!). The answer appears to be non-obvious, as so far none of my correspondents has come up with an answer (including most recently two CS profs). Or maybe I'm missing something that's so obvious that people can't imagine my not knowing it... I've added the send and receive code here - not very elegant, but it seems to work...;-) In case you are wondering, I thought the goLock logic in 'send' might be causing the problem, but removing it temporarily didn't make any difference. I have added the code for send and receive... public synchronized Packet receive() { if (isDrained()) { return null; } while (isEmpty()) { try { wait(); } catch (InterruptedException e) { close(); return null; } if (isDrained()) { return null; } } if (isDrained()) { return null; } if (isFull()) { notifyAll(); // notify other components waiting to send } Packet packet = array[receivePtr]; array[receivePtr] = null; receivePtr = (receivePtr + 1) % array.length; //notifyAll(); // only needed if it was full usedSlots--; packet.setOwner(receiver); if (null == packet.getContent()) { traceFuncs("Received null packet"); } else { traceFuncs("Received: " + packet.toString()); } return packet; } synchronized boolean send(final Packet packet, final OutputPort op) { sender = op.sender; if (isClosed()) { return false; } while (isFull()) { try { wait(); } catch (InterruptedException e) { indicateOneSenderClosed(); return false; } sender = op.sender; } if (isClosed()) { return false; } try { receiver.goLock.lockInterruptibly(); } catch (InterruptedException ex) { return false; } try { packet.clearOwner(); array[sendPtr] = packet; sendPtr = (sendPtr + 1) % array.length; usedSlots++; // move this to here if (receiver.getStatus() == StatusValues.DORMANT || receiver.getStatus() == StatusValues.NOT_STARTED) { receiver.activate(); // start or wake up if necessary } else { notifyAll(); // notify receiver // other components waiting to send to this connection may also get // notified, // but this is handled by while statement } sender = null; Component.network.active = true; } finally { receiver.goLock.unlock(); } return true; }

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  • Python: Socket set source port number

    - by beratch
    Hi all, I'd like to send a specific UDP broadcast packet.. unfortunatly i need to send the udp packet from a very specific port for all packet I send. Let say I broadcast via UDP "BLABLAH", the server will only answer if my incoming packet source port was 1444, if not the packet is discarded. My broadcast socket setup look like this : s = socket(AF_INET,SOCK_DGRAM) s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1) How can i do that (set the source port) in python ? Thanks!

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  • C# listview add items

    - by Eyla
    Greetings, I have a method to capture packets. after capturing I want to add each packet as a row in listview in runting time so as soon as I capture packet I want to add it to the list view. the problem that when I use items.Add() I will get overload argument error. please advice!! here is my code: private void packetCapturingThreadMethod() { Packet packet = null; int countOfPacketCaptures = 0; while ((packet = device.GetNextPacket()) != null) { packet = device.GetNextPacket(); if (packet is TCPPacket) { TCPPacket tcp = (TCPPacket)packet; myPacket tempPacket = new myPacket(); tempPacket.packetType = "TCP"; tempPacket.sourceAddress = Convert.ToString(tcp.SourceAddress); tempPacket.destinationAddress = Convert.ToString(tcp.DestinationAddress); tempPacket.sourcePort = Convert.ToString(tcp.SourcePort); tempPacket.destinationPort = Convert.ToString(tcp.DestinationPort); tempPacket.packetMessage = Convert.ToString(tcp.Data); packetsList.Add(tempPacket); string[] row = { packetsList[countOfPacketCaptures].packetType, packetsList[countOfPacketCaptures].sourceAddress, packetsList[countOfPacketCaptures].destinationAddress, packetsList[countOfPacketCaptures].sourcePort, packetsList[countOfPacketCaptures].destinationPort, packetsList[countOfPacketCaptures].packetMessage }; try { listView1.Items.Add(packetsList[countOfPacketCaptures].packetType, packetsList[countOfPacketCaptures].sourceAddress, packetsList[countOfPacketCaptures].destinationAddress, packetsList[countOfPacketCaptures].sourcePort, packetsList[countOfPacketCaptures].destinationPort, packetsList[countOfPacketCaptures].packetMessage) ; countOfPacketCaptures++; lblCapturesLabels.Text = Convert.ToString(countOfPacketCaptures);} catch (Exception e) { } } else if (packet is UDPPacket) { UDPPacket udp = (UDPPacket)packet; myPacket tempPacket = new myPacket(); tempPacket.packetType = "UDP"; tempPacket.sourceAddress = Convert.ToString(udp.SourceAddress); tempPacket.destinationAddress = Convert.ToString(udp.DestinationAddress); tempPacket.sourcePort = Convert.ToString(udp.SourcePort); tempPacket.destinationPort = Convert.ToString(udp.DestinationPort); tempPacket.packetMessage = Convert.ToString(udp.Data); packetsList.Add(tempPacket); string[] row = { packetsList[countOfPacketCaptures].packetType, packetsList[countOfPacketCaptures].sourceAddress, packetsList[countOfPacketCaptures].destinationAddress, packetsList[countOfPacketCaptures].sourcePort, packetsList[countOfPacketCaptures].destinationPort, packetsList[countOfPacketCaptures].packetMessage }; try { dgwPacketInfo.Rows.Add(row); countOfPacketCaptures++; lblCapturesLabels.Text = Convert.ToString(countOfPacketCaptures); } catch (Exception e) { } } } }

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  • Python and libpcap. find source mac address of packet.

    - by Shamanu4
    Hello! I'm writing python program to build mac-address cache using pcap. But pcap module for python has no good documentation. I have found this page http://pylibpcap.sourceforge.net/ with code example and it works fine. Can anybody modify this example to make it able to show the source mac-address for each packet? Or point me to the documentation where I can read about it ...

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  • How do I modify a HTTP response packet with winpcap?

    - by httpinterpret
    There are two problems here: What if content is encoded:gzip... Do I also need to change the header part to make the HTTP packet valid(checksums if any?) UPDATE Can someone with actual experience elaborate the steps involved? I'm using winpcap and bpf tcp and src port 80 to filter the traffic,so my job lies in this callback function: void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data)

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  • What are the best authentication and authorization examples for your favorite web framework?

    - by Nathan Feger
    I have been looking through java web frameworks lately (though this question need not be limited to java), and I noticed that most examples on web framework websites leave out auth & auth examples in their stock documentation. one ruby example: acts_as_authenticated (link?) grails has: http://www.grails.org/Authentication+Plugin Anyway, please throw up some links to your framework of choice, and a link to a nice walkthrough to implementing an auth&auth solution.

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