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  • IEnumerable<T> ToArray usage, is it a copy or a pointer?

    - by Daniel
    I am parsing an arbitrary length byte array that is going to be passed around to a few different layers of parsing. Each parser creates a Header and a Packet payload just like any ordinary encapsulation. And my problem lies in how the encapsulation holds its packet byte array payload. Say i have a 100 byte array, and it has 3 levels of encapsulation. 3 packet objects will be created and i want to set the payload of these packets to the corresponding position in the byte array of the packet. For example lets say the payload size is 20 for all levels, then imagine it has a public byte[] Payload on each object. However the problem is that this byte[] Payload is a copy of the original 100 bytes. So i'm going to end up with 160 bytes in memory instead of 100. If it were in c++ i could just easily use a pointer however i'm writing this in c#. So i created the following class: public class PayloadSegment<T> : IEnumerable<T> { public readonly T[] Array; public readonly int Offset; public readonly int Count; public PayloadSegment(T[] array, int offset, int count) { this.Array = array; this.Offset = offset; this.Count = count; } public T this[int index] { get { if (index < 0 || index >= this.Count) throw new IndexOutOfRangeException(); else return Array[Offset + index]; } set { if (index < 0 || index >= this.Count) throw new IndexOutOfRangeException(); else Array[Offset + index] = value; } } public IEnumerator<T> GetEnumerator() { for (int i = Offset; i < Offset + Count; i++) yield return Array[i]; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { IEnumerator<T> enumerator = this.GetEnumerator(); while (enumerator.MoveNext()) { yield return enumerator.Current; } } } This way i can simply reference a position inside the original byte array but use positional indexing. However if i do something like: PayloadSegment<byte> something = new PayloadSegment<byte>(someArray, 5, 10); byte[] somethingArray = something.ToArray(); Will the somethingArray be a copy of the bytes, or a reference to the original PayloadSegment which in turn is a reference to the original byte array? Sorry it was hard to word this lol _<

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  • Port forwarding in C#/software possible? Isn't it only managed by the router?

    - by Rudi
    Isn't port forwarding managed by the router? Like, I've googled up some software applications that seem to port forward with great success, but it technically seems to be impossible. The packet must first go to the router. The router must forward it to the correct computer based on port forwarding rules. So how can a software application manage port forwarding if the packet must GO to the computer running this software application in the first place, meaning that port forwarding already is successful in the first place?

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  • How do you return stolen packets back to Netfilter

    - by meg18019
    Let's say I have intercepted a packet from Netfilter and subsequently returned NF_STOLEN. At some point I want to re-inject that packet back to, in this case, the TCP stream it came from. I want to do this from Kernel space. So far I have been unable to find a way to do this. Thanks for the help.

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  • Hibernate Communications Link Failure in Restlet-Hibernate Based Java application powered by MySQL

    - by Vatsala
    Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?)

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  • What does this pointer-heavy C code do?

    - by justRadojko
    Could someone explain to me what should two following lines do: s.httpheaderline[s.httpheaderlineptr] = *(char *)uip_appdata; ++((char *)uip_appdata); This is taken from uIP code for microcontrollers. s - structure httpheaderline - http packet presented as a string httpheadrlineptr - integer value uip_appdata - received ethernet packet (string) If some more info is needed please let me know. BTW. Eclipse is reporting an error on the second line with message Invalid lvalue in increment so i'm trying to figure out how to solve this.

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  • TCP Connection Persistent State

    - by TripShock
    Is there any field/option/anything that I can put in a TCP packet (be it a syn or an ack or just plain data) that I can be sure will be returned by the other end intact? For eg. I want to "tag" a particular connection (src, srcport, dst, dstport) with a number that I can always read from a packet belonging to that connection. That means I can identify the connection without using the 4-tuple (as given above).

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  • PPPTP VPN from Ubuntu cannot connect

    - by Andrea Polci
    I'm trying to configure under Linux (Kubuntu 9.10) a VPN I already use from Windows. I installed the network-manager-pptp package and added the vpn under Network Manager. These are the parameter under "advanced" button: Authentication Methods: PAP, CHAP, MSCHAP, SMCHAP2, EAP (I tried also with MSCHAP and MSCHAP2 only) Use MPPE Encryption: yes Crypto: Any Use stateful encryption: no Compression: Allow BSD compression: yes Allow Deflate compression: yes Allow TCP header compression: yes Send PPP echo packets: no When I try to connnect it doesn't work and this is what I get in the system log: 2010-04-08 13:53:47 pcelena NetworkManager <info> Starting VPN service 'org.freedesktop.NetworkManager.pptp'... 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN service 'org.freedesktop.NetworkManager.pptp' started (org.freedesktop.NetworkManager.pptp), PID 4931 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN service 'org.freedesktop.NetworkManager.pptp' just appeared, activating connections 2010-04-08 13:53:47 pcelena pppd[4932] Plugin /usr/lib/pppd/2.4.5//nm-pptp-pppd-plugin.so loaded. 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN plugin state changed: 3 2010-04-08 13:53:47 pcelena pppd[4932] pppd 2.4.5 started by root, uid 0 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN connection 'MYVPN' (Connect) reply received. 2010-04-08 13:53:47 pcelena NetworkManager SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0) 2010-04-08 13:53:47 pcelena NetworkManager SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found. 2010-04-08 13:53:47 pcelena pppd[4932] Using interface ppp0 2010-04-08 13:53:47 pcelena pppd[4932] Connect: ppp0 <--> /dev/pts/2 2010-04-08 13:53:47 pcelena pptp[4934] nm-pptp-service-4931 log[main:pptp.c:314]: The synchronous pptp option is NOT activated 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request' 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply. 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 1, peer's call ID 14800). 2010-04-08 13:53:48 pcelena pppd[4932] CHAP authentication succeeded 2010-04-08 13:53:48 pcelena pppd[4932] CHAP authentication succeeded 2010-04-08 13:53:48 pcelena pppd[4932] LCP terminated by peer 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:929]: Call disconnect notification received (call id 14800) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:788]: Received Stop Control Connection Request. 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 4 'Stop-Control-Connection-Reply' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[callmgr_main:pptp_callmgr.c:258]: Closing connection (shutdown) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[callmgr_main:pptp_callmgr.c:258]: Closing connection (shutdown) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state) 2010-04-08 13:53:48 pcelena pppd[4932] Modem hangup 2010-04-08 13:53:48 pcelena pppd[4932] Connection terminated. 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin failed: 1 2010-04-08 13:53:48 pcelena NetworkManager SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0) 2010-04-08 13:53:48 pcelena pppd[4932] Exit. 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin failed: 1 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin state changed: 6 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin state change reason: 0 2010-04-08 13:53:48 pcelena NetworkManager <WARN> connection_state_changed(): Could not process the request because no VPN connection was active. 2010-04-08 13:53:48 pcelena NetworkManager <info> Policy set 'Auto eth0' (eth0) as default for routing and DNS. 2010-04-08 13:54:01 pcelena NetworkManager <debug> [1270727641.001390] ensure_killed(): waiting for vpn service pid 4931 to exit 2010-04-08 13:54:01 pcelena NetworkManager <debug> [1270727641.001479] ensure_killed(): vpn service pid 4931 cleaned up Does anyone has suggestion on what can be the problem and how to make it work?

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  • PPTP VPN from Ubuntu cannot connect

    - by Andrea Polci
    I'm trying to configure under Linux (Kubuntu 9.10) a VPN I already use from Windows. I installed the network-manager-pptp package and added the VPN under Network Manager. These are the parameters under "advanced" button: Authentication Methods: PAP, CHAP, MSCHAP, MSCHAP2, EAP (I also tried "MSCHAP, MSCHAP2") Use MPPE Encryption: yes Crypto: Any Use stateful encryption: no Allow BSD compression: yes Allow Deflate compression: yes Allow TCP header compression: yes Send PPP echo packets: no When I try to connnect it doesn't work and this is what I get in the system log: 2010-04-08 13:53:47 pcelena NetworkManager <info> Starting VPN service 'org.freedesktop.NetworkManager.pptp'... 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN service 'org.freedesktop.NetworkManager.pptp' started (org.freedesktop.NetworkManager.pptp), PID 4931 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN service 'org.freedesktop.NetworkManager.pptp' just appeared, activating connections 2010-04-08 13:53:47 pcelena pppd[4932] Plugin /usr/lib/pppd/2.4.5//nm-pptp-pppd-plugin.so loaded. 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN plugin state changed: 3 2010-04-08 13:53:47 pcelena pppd[4932] pppd 2.4.5 started by root, uid 0 2010-04-08 13:53:47 pcelena NetworkManager <info> VPN connection 'MYVPN' (Connect) reply received. 2010-04-08 13:53:47 pcelena NetworkManager SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0) 2010-04-08 13:53:47 pcelena NetworkManager SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found. 2010-04-08 13:53:47 pcelena pppd[4932] Using interface ppp0 2010-04-08 13:53:47 pcelena pppd[4932] Connect: ppp0 <--> /dev/pts/2 2010-04-08 13:53:47 pcelena pptp[4934] nm-pptp-service-4931 log[main:pptp.c:314]: The synchronous pptp option is NOT activated 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request' 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply. 2010-04-08 13:53:47 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 1, peer's call ID 14800). 2010-04-08 13:53:48 pcelena pppd[4932] CHAP authentication succeeded 2010-04-08 13:53:48 pcelena pppd[4932] CHAP authentication succeeded 2010-04-08 13:53:48 pcelena pppd[4932] LCP terminated by peer 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:929]: Call disconnect notification received (call id 14800) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_disp:pptp_ctrl.c:788]: Received Stop Control Connection Request. 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 4 'Stop-Control-Connection-Reply' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[callmgr_main:pptp_callmgr.c:258]: Closing connection (shutdown) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[callmgr_main:pptp_callmgr.c:258]: Closing connection (shutdown) 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' 2010-04-08 13:53:48 pcelena pptp[4927] nm-pptp-service-4918 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state) 2010-04-08 13:53:48 pcelena pppd[4932] Modem hangup 2010-04-08 13:53:48 pcelena pppd[4932] Connection terminated. 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin failed: 1 2010-04-08 13:53:48 pcelena NetworkManager SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0) 2010-04-08 13:53:48 pcelena pppd[4932] Exit. 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin failed: 1 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin state changed: 6 2010-04-08 13:53:48 pcelena NetworkManager <info> VPN plugin state change reason: 0 2010-04-08 13:53:48 pcelena NetworkManager <WARN> connection_state_changed(): Could not process the request because no VPN connection was active. 2010-04-08 13:53:48 pcelena NetworkManager <info> Policy set 'Auto eth0' (eth0) as default for routing and DNS. 2010-04-08 13:54:01 pcelena NetworkManager <debug> [1270727641.001390] ensure_killed(): waiting for vpn service pid 4931 to exit 2010-04-08 13:54:01 pcelena NetworkManager <debug> [1270727641.001479] ensure_killed(): vpn service pid 4931 cleaned up The error that sticks out here is "pppd[4932] LCP terminated by peer". Does anyone has suggestion on what can be the problem and how to make it work?

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  • Ubuntu 12.04 + Wifi not working

    - by user171154
    i'm having problems connecting over wireless. At the moment, I'm using wicd. It seems to get stuck on "Verifying AP association...". Without wicd I can get the connection up and ping the Net - but if I take eth0 down (ifconfig eth0 down), my wireless goes away too (same result if I unplug the wire instead). wicd is the only way I can bring eth0 back (which is the main reason I'm using it) - ifconfig eth0 and/or ifup eth0 do not re-enable the connection (I just discovered it leaves out the gateway. Adding the gateway back in re-enables the connection including wifi; I didn't want to delete the info about wicd above in case it gives someone an idea.) Doing it manually, despite the errors (which it would be nice to also resolve) - allows me to ping the outside world: ifup wlan0 ioctl[SIOCSIWENCODEEXT]: Invalid argument ioctl[SIOCSIWENCODEEXT]: Invalid argument ssh stop/waiting ssh start/running, process 17336 ping -I wlan0 -c 4 8.8.8.8 PING 8.8.8.8 (8.8.8.8) from 192.168.0.12 wlan0: 56(84) bytes of data. 64 bytes from 8.8.8.8: icmp_req=1 ttl=43 time=48.8 ms 64 bytes from 8.8.8.8: icmp_req=2 ttl=43 time=47.9 ms 64 bytes from 8.8.8.8: icmp_req=3 ttl=43 time=48.7 ms 64 bytes from 8.8.8.8: icmp_req=4 ttl=43 time=53.2 ms --- 8.8.8.8 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3003ms rtt min/avg/max/mdev = 47.975/49.711/53.235/2.063 ms # iwconfig lo no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"TPLINK" Mode:Managed Frequency:2.427 GHz Access Point: 64:66:xx:xx:xx:22 Bit Rate=108 Mb/s Tx-Power=27 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off Link Quality=70/70 Signal level=-39 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:3 Missed beacon:0 bus info: pci@0000:03:00.0 logical name: wlan0 version: 01 serial: f0:7d:68:c1:b4:13 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=ath9k driverversion=3.2.0-67-generic-pae firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn resources: irq:17 memory:dfbf0000-dfbfffff ip route default via 192.168.0.1 dev eth0 default via 192.168.0.1 dev wlan0 metric 100 169.254.0.0/16 dev wlan0 scope link metric 1000 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.102 192.168.0.0/24 dev wlan0 proto kernel scope link src 192.168.0.12 (For the record, I have no idea what the 169.254.0.0 address is doing there.) uname -a 3.2.0-67-generic-pae #101-Ubuntu SMP Tue Jul 15 18:04:54 UTC 2014 i686 i686 i386 GNU/Linux lshw -C network *-network description: Ethernet interface product: NetXtreme BCM5751 Gigabit Ethernet PCI Express vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: 01 serial: 00:11:11:59:fc:09 size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 duplex=full firmware=5751-v3.23a ip=192.168.0.102 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s resources: irq:16 memory:dfcf0000-dfcfffff *-network description: Wireless interface product: AR5418 Wireless Network Adapter [AR5008E 802.11(a)bgn] (PCI-Express) vendor: Qualcomm Atheros physical id: 0 /etc/network/interfaces # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback source /etc/network/interfaces.eth0 source /etc/network/interfaces.wlan0 /etc/network/interfaces.eth0 #Main Interface auto eth0 iface eth0 inet static address 192.168.0.102 netmask 255.255.255.0 gateway 192.168.0.1 /etc/network/interfaces.wlan0 auto wlan0 iface wlan0 inet static address 192.168.0.12 gateway 192.168.0.1 dns-nameservers 192.168.0.1 8.8.8.8 netmask 255.255.255.0 wpa-driver wext wpa-ssid TPLINK wpa-ap-scan 1 wpa-proto RSN wpa-pairwise CCMP wpa-group CCMP wpa-key-mgmt WPA-PSK wpa-psk dca1badb5fd4e9axxx4xxdaaxxfa91xx610bxx6a7d57ef67af9809dxx6af42e39 /etc/wpa_supplicant.conf ctrl_interface=/var/run/wpa_supplicant network={ ssid="TPLINK" psk="my password" key_mgmt=WPA-PSK proto=RSN pairwise=CCMP group=CCMP } ifdown eth0 ifdown: interface eth0 not configured ifconfig eth0 Link encap:Ethernet HWaddr 00:11:xx:xx:xx:09 inet addr:192.168.0.102 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::211:11ff:fe59:fc09/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:213690 errors:0 dropped:0 overruns:0 frame:0 TX packets:155266 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:220057808 (220.0 MB) TX bytes:21137696 (21.1 MB) Interrupt:16 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:196412 errors:0 dropped:0 overruns:0 frame:0 TX packets:196412 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:153270697 (153.2 MB) TX bytes:153270697 (153.2 MB) wlan0 Link encap:Ethernet HWaddr f0:7d:xx:xx:xx:13 inet addr:192.168.0.12 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::f27d:68ff:fec1:b413/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11335 errors:0 dropped:0 overruns:0 frame:0 TX packets:7287 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2563290 (2.5 MB) TX bytes:855746 (855.7 KB) ifconfig eth0 down ifconfig eth0 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:09 inet addr:192.168.0.102 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::211:11ff:fe59:fc09/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2 errors:0 dropped:0 overruns:0 frame:0 TX packets:1 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:192 (192.0 B) TX bytes:94 (94.0 B) Interrupt:16 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:196418 errors:0 dropped:0 overruns:0 frame:0 TX packets:196418 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:153270871 (153.2 MB) TX bytes:153270871 (153.2 MB) wlan0 Link encap:Ethernet HWaddr f0:7d:xx:xx:xx:13 inet addr:192.168.0.12 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::f27d:68ff:fec1:b413/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11359 errors:0 dropped:0 overruns:0 frame:0 TX packets:7293 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2565482 (2.5 MB) TX bytes:856363 (856.3 KB) ip route default via 192.168.0.1 dev wlan0 metric 100 169.254.0.0/16 dev wlan0 scope link metric 1000 192.168.0.0/24 dev wlan0 proto kernel scope link src 192.168.0.12 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.102 ping -I wlan0 -c 4 8.8.8.8 PING 8.8.8.8 (8.8.8.8) from 192.168.0.12 wlan0: 56(84) bytes of data. --- 8.8.8.8 ping statistics --- 4 packets transmitted, 0 received, 100% packet loss, time 3024ms ping -I eth0 -c 3 router PING router (192.168.0.1) from 192.168.0.102 eth0: 56(84) bytes of data. --- router ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2015ms ping -I wlan0 -c 3 router PING router (192.168.0.1) from 192.168.0.12 wlan0: 56(84) bytes of data. --- router ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2014ms Let me know if you need more info. Thank you in advance.

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  • Wireless is detected, but not connecting. Ethernet works. How to correct the wireless address?

    - by Lucas
    I am running Ubuntu 14.04 with cable internet, and my wireless is detected and connected, but I cannot connect to the internet. I know the problem is with my machine because other machines are connecting to the same router just fine. I can connect via ethernet just fine as well. Here are some notable tests: ping 192.168.0.105 works with 0% packet loss, but ping 192.168.0.1 has 100% packet loss. When I plug in my ethernet, ping 192.168.0.1 works with 0% packet loss. My wireless name is tg, and the router ip is 192.168.0.1 (where I can enter username and password). I suspect that I need to change my wireless address from 192.168.0.105 to 192.168.0.1. Any suggestions on how to proceed? extra info: [lucas@lucas-ThinkPad-W520]/home/lucas$ iwconfig eth0 no wireless extensions. lo no wireless extensions. wlan0 IEEE 802.11abgn ESSID:"tg" Mode:Managed Frequency:2.462 GHz Access Point: 00:02:6F:83:F8:F4 Bit Rate=1 Mb/s Tx-Power=15 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=62/70 Signal level=-48 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:52 Invalid misc:166 Missed beacon:0 [lucas@lucas-ThinkPad-W520]/home/lucas$ ifconfig eth0 Link encap:Ethernet HWaddr f0:de:f1:b2:53:53 inet addr:192.168.0.100 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::f2de:f1ff:feb2:5353/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:980003 errors:0 dropped:0 overruns:0 frame:0 TX packets:498384 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1320506168 (1.3 GB) TX bytes:59780591 (59.7 MB) Interrupt:20 Memory:f3a00000-f3a20000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:21927 errors:0 dropped:0 overruns:0 frame:0 TX packets:21927 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1781719 (1.7 MB) TX bytes:1781719 (1.7 MB) wlan0 Link encap:Ethernet HWaddr 24:77:03:29:8f:dc inet addr:192.168.0.105 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::2677:3ff:fe29:8fdc/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11828 errors:0 dropped:0 overruns:0 frame:0 TX packets:15444 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4855662 (4.8 MB) TX bytes:2250585 (2.2 MB) [lucas@lucas-ThinkPad-W520]/home/lucas$ lspci -nn | grep 0280 03:00.0 Network controller [0280]: Intel Corporation Centrino Ultimate-N 6300 [8086:4238] (rev 3e) [lucas@lucas-ThinkPad-W520]/home/lucas$ rfkill list 0: hci0: Bluetooth Soft blocked: no Hard blocked: no 1: tpacpi_bluetooth_sw: Bluetooth Soft blocked: no Hard blocked: no 2: phy0: Wireless LAN Soft blocked: no Hard blocked: no with ethernet unplugged: [lucas@lucas-ThinkPad-W520]/home/lucas$ route -n | grep UG 0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 wlan0 with ethernet plugged in: [lucas@lucas-ThinkPad-W520]/home/lucas$ route -n | grep UG 0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth0 [lucas@lucas-ThinkPad-W520]/home/lucas$ nm-tool NetworkManager Tool State: connected (global) - Device: wlan0 [tg] ---------------------------------------------------------- Type: 802.11 WiFi Driver: iwlwifi State: connected Default: no HW Address: 24:77:03:29:8F:DC Capabilities: Speed: 52 Mb/s Wireless Properties WEP Encryption: yes WPA Encryption: yes WPA2 Encryption: yes Wireless Access Points (* = current AP) tatum: Infra, 40:8B:07:D8:A5:04, Freq 2437 MHz, Rate 54 Mb/s, Strength 42 W PA WPA2 ums: Infra, 00:20:A6:72:52:BF, Freq 2437 MHz, Rate 54 Mb/s, Strength 59 Alpha 40: Infra, 28:CF:E9:86:59:5D, Freq 5260 MHz, Rate 54 Mb/s, Strength 30 W PA WPA2 thepromiselan: Infra, 58:6D:8F:51:E5:54, Freq 2452 MHz, Rate 54 Mb/s, Strength 34 $ PA WPA2 xfinitywifi: Infra, 06:1D:D5:84:27:A0, Freq 2437 MHz, Rate 54 Mb/s, Strength 52 *tg: Infra, 00:02:6F:83:F8:F4, Freq 2462 MHz, Rate 54 Mb/s, Strength 73 W PA2 ums: Infra, 00:20:A6:A1:9F:25, Freq 2452 MHz, Rate 54 Mb/s, Strength 44 BRIAN-PC_Network:Infra, 20:AA:4B:DD:93:D6, Freq 2462 MHz, Rate 54 Mb/s, Strength 35 W PA2 HOME-C0F8: Infra, 44:32:C8:D2:C0:F8, Freq 2412 MHz, Rate 54 Mb/s, Strength 40 W PA WPA2 abcsexy: Infra, 28:28:5D:27:5D:85, Freq 2412 MHz, Rate 54 Mb/s, Strength 27 W PA WPA2 IPv4 Settings: Address: 192.168.0.105 Prefix: 24 (255.255.255.0) Gateway: 192.168.0.1 DNS: 192.168.0.1 - Device: eth0 [Wired connection 1] ------------------------------------------- Type: Wired Driver: e1000e State: connected Default: yes HW Address: F0:DE:F1:B2:53:53 Capabilities: Carrier Detect: yes Speed: 100 Mb/s Wired Properties Carrier: on IPv4 Settings: Address: 192.168.0.100 Prefix: 24 (255.255.255.0) Gateway: 192.168.0.1 DNS: 192.168.0.1

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  • Can't connect to VPN on Ubuntu 12.04

    - by 12rad
    I'm having a lot of trouble connecting to VPN. This used to work on my machine, but i recently did an update and it's stopped working. I'm not sure what the problem is. My question is how do i debug this? I'm not able to narrow it down to a specific problem. This is what i get when i tail the syslogs. Would appreciate any help! Nov 6 23:42:52 meera NetworkManager[1137]: <info> Starting VPN service 'pptp'... Nov 6 23:42:52 meera NetworkManager[1137]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 6132 Nov 6 23:42:52 meera NetworkManager[1137]: <info> VPN service 'pptp' appeared; activating connections Nov 6 23:42:52 meera NetworkManager[1137]: <info> VPN plugin state changed: starting (3) Nov 6 23:42:52 meera NetworkManager[1137]: <info> VPN connection 'NAME VPN' (Connect) reply received. Nov 6 23:42:52 meera pppd[6136]: Plugin /usr/lib/pppd/2.4.5/nm-pptp-pppd-plugin.so loaded. Nov 6 23:42:52 meera pppd[6136]: pppd 2.4.5 started by root, uid 0 Nov 6 23:42:52 meera chat[6139]: timeout set to 15 seconds Nov 6 23:42:52 meera chat[6139]: abort on (NO CARRIER) Nov 6 23:42:52 meera chat[6139]: abort on (NO DIALTONE) Nov 6 23:42:52 meera chat[6139]: abort on (ERROR) Nov 6 23:42:52 meera chat[6139]: abort on (NO ANSWER) Nov 6 23:42:52 meera chat[6139]: abort on (BUSY) Nov 6 23:42:52 meera chat[6139]: abort on (Username/Password Incorrect) Nov 6 23:42:52 meera chat[6139]: send (AT^M) Nov 6 23:42:52 meera pptp[6138]: nm-pptp-service-6132 log[main:pptp.c:314]: The synchronous pptp option is NOT activated Nov 6 23:42:52 meera chat[6139]: expect (OK) Nov 6 23:42:52 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request' Nov 6 23:42:53 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply Nov 6 23:42:53 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established. Nov 6 23:42:53 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request' Nov 6 23:42:54 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_disp:pptp_ctrl.c:858]: Received Outgoing Call Reply. Nov 6 23:42:54 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_disp:pptp_ctrl.c:897]: Outgoing call established (call ID 0, peer's call ID 13077). Nov 6 23:42:54 meera pptp[6138]: nm-pptp-service-6132 warn[decaps_hdlc:pptp_gre.c:231]: The ppp mode is synchronous, yet no pptp --sync option is specified! Nov 6 23:43:07 meera chat[6139]: alarm Nov 6 23:43:07 meera chat[6139]: Failed Nov 6 23:43:07 meera pppd[6136]: Script chat -v -f /etc/ppp/chat-ztisp finished (pid 6139), status = 0x3 Nov 6 23:43:07 meera pppd[6136]: Connect script failed Nov 6 23:43:07 meera pppd[6136]: Waiting for 1 child processes... Nov 6 23:43:07 meera pppd[6136]: script /usr/sbin/pptp 204.197.218.90 --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-6132, pid 6138 Nov 6 23:43:07 meera pptp[6138]: nm-pptp-service-6132 warn[decaps_hdlc:pptp_gre.c:204]: short read (-1): Input/output error Nov 6 23:43:07 meera pptp[6138]: nm-pptp-service-6132 warn[decaps_hdlc:pptp_gre.c:216]: pppd may have shutdown, see pppd log Nov 6 23:43:07 meera pptp[6143]: nm-pptp-service-6132 log[callmgr_main:pptp_callmgr.c:234]: Closing connection (unhandled) Nov 6 23:43:07 meera pppd[6136]: Script /usr/sbin/pptp 204.197.218.90 --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-6132 finished (pid 6138), status = 0x0 Nov 6 23:43:07 meera pptp[6143]: nm-pptp-service-6132 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 12 'Call-Clear-Request' Nov 6 23:43:07 meera pptp[6143]: nm-pptp-service-6132 log[call_callback:pptp_callmgr.c:79]: Closing connection (call state) Nov 6 23:43:07 meera pppd[6136]: Exit. Nov 6 23:43:07 meera NetworkManager[1137]: <warn> VPN plugin failed: 1 Nov 6 23:43:07 meera NetworkManager[1137]: <info> VPN plugin state changed: stopped (6) Nov 6 23:43:07 meera NetworkManager[1137]: <info> VPN plugin state change reason: 0 Nov 6 23:43:07 meera NetworkManager[1137]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.

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  • Decoding tcp packets using python

    - by mikip
    Hello I am trying to decode data received over a tcp connection. The packets are small, no more than 100 bytes. However when there is a lot of them I receive some of the the packets joined together. Is there a way to prevent this. I am using python I have tried to separate the packets, my source is below. The packets start with STX byte and end with ETX bytes, the byte following the STX is the packet length, (packet lengths less than 5 are invalid) the checksum is the last bytes before the ETX def decode(data): while True: start = data.find(STX) if start == -1: #no stx in message pkt = '' data = '' break #stx found , next byte is the length pktlen = ord(data[1]) #check message ends in ETX (pktken -1) or checksum invalid if pktlen < 5 or data[pktlen-1] != ETX or checksum_valid(data[start:pktlen]) == False: print "Invalid Pkt" data = data[start+1:] continue else: pkt = data[start:pktlen] data = data[pktlen:] break return data , pkt I use it like this #process reports try: data = sock.recv(256) except: continue else: while data: data, pkt = decode(data) if pkt: process(pkt) Also if there are multiple packets in the data stream, is it best to return the packets as a collection of lists or just return the first packet I am not that familiar with python, only C, is this method OK. Any advice would be most appreciated. Thanks in advance Thanks

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  • error detection/correction/recovery in serial protocols

    - by Jason S
    I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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  • How frequently IP packets are fragmented at the source host?

    - by Methos
    I know that if IP payload MTU then routers usually fragment the IP packet. Finally all the fragmented packets are assembled at the destination using the fields IP-ID, IP fragment offsets and fragmentation flags. Max length of IP payload is 64K. Thus its very plausible for L4 to hand over payload which is 64K. If the L2 protocol is Ethernet, which often is the case, then the MTU will be about 1600 bytes. Hence IP packet will be fragmented at the source host itself. However, a quick search about IP implementation in Linux tells me that in recent kernels, L4 protocols are fragment friendly i.e. they try to save the fragmentation work for IP by handing over buffers of size which is close to MTU. Considering these two facts, I am wondering about how frequently does the IP packet gets fragmented at the source host itself. Does it occur sometimes/rarely/never? Does anyone know if there are exceptions to the rule of fragmentation in linux kernel (i.e. are there situations where L4 protocols are not fragment friendly)? How is this handled in other common OSes like windows? In general how frequently IP packets are fragmented?

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  • How to synchronize Silverlight clients with WCF?

    - by user564226
    Hi, this is probably only some conceptual problem, but I cannot seem to find the ideal solution. I'd like to create a Silverlight client application that uses WCF to control a third party application via some self written webservice. If there is more than one Silverlight client, all clients should be synchronized, i.e. parameter changes from one client should be propagated to all clients. I set up a very simple Silverlight GUI that manipulates parameters which are passed to the server (class inherits INotifyPropertyChanged): public double Height { get { return frameworkElement.Height; } set { if (frameworkElement.Height != value) { frameworkElement.Height = value; OnPropertyChanged("Height", value); } } } OnPropertyChanged is responsible for transferring data. The WCF service (duplex net.tcp) maintains a list of all clients and as soon as it receives a data packet (XElement with parameter change description) it forwards this very packet to all clients but the one the packet was received from. The client receives the package, but now I'm not sure, what's the best way to set the property internally. If I use "Height" (see above) a new change message would be generated and sent to all other clients a.s.o. Maybe I could use the data field (frameworkElement.Height) itself or a function - but I'm not sure whether there would arise problems with data binding later on. Also I don't want to simply copy parts of the code properties, to prevent bugs with redundant code. So what would you recommend? Thanks!

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  • Best practices for encrypting continuous/small UDP data

    - by temp
    Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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  • Best practices for encrytping continuous/small UDP data

    - by temp
    Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (on waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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  • Is this the right way to write a ProtocolDecoder in MINA?

    - by phpscriptcoder
    public class CustomProtocolDecoder extends CumulativeProtocolDecoder{ byte currentCmd = -1; int currentSize = -1; boolean isFirst = false; @Override protected boolean doDecode(IoSession is, ByteBuffer bb, ProtocolDecoderOutput pdo) throws Exception { if(currentCmd == -1) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); isFirst = true; } while(bb.remaining() > 0) { if(!isFirst) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); } else isFirst = false; //System.err.println(currentCmd + " " + bb.remaining() + " " + currentSize); if(bb.remaining() >= currentSize - 1) { Packet p = PacketDecoder.decodePacket(bb, currentCmd); pdo.write(p); } else { bb.flip(); return false; } } if(bb.remaining() == 0) return true; else return false; } } Anyone see anything wrong with this code? When a lot of packets are received at once, even when only one client is connected, one of them might get cut off at the end (12 bytes instead of 15 bytes, for example) which is obviously bad.

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  • [java] tcp socket communication [send and recieve help]

    - by raven
    hello, I am creating a Chat in java. I have a method (onMouseRelease) inside an object that creates a tcp server and waits for a socket ServerSocket server = new ServerSocket(port); Socket channel = server.accept(); now I want to make a thread that will loop and read data from the socket, so that once the user on the other side sent me a string, I will extract the data from the socket [or is it called packet? sry I am new to this], and update a textbox to add the additional string from the socket [or packet?]. I have no idea how to READ (extract) the information from the scoket [/packet] and then update it into a JTextArea which is called userOutput. And how to Send a string to the other client, so that it will also could read the new data and update its JTextArea. (from what I know, for a 2 sided tcp communication you need one computer to host a server and the other to connect [as a client] and once the connection is set the client can also recieve new information from the socket. Is that true? and please tell me how ) Any help appreciated !! I know this is abit long but I have searched allot and didn't understand [I saw something like printwriter but failed to understand].

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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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  • Java if/else behaving strangely

    - by Alex
    I'm a real newbie to java, so please excuse me if this is a hopelessly straightforward problem. I have the following from my java game server: // Get input from the client DataInputStream in = new DataInputStream (server.getInputStream()); PrintStream out = new PrintStream(server.getOutputStream()); disconnect=false; while((line = in.readLine().trim()) != null && !line.equals(".") && !line.equals("") && !disconnect) { System.out.println("Received "+line); if(line.equals("h")){ out.println("h"+EOF); // Client handshake System.out.println("Matched 1"); }else if (line.equals("<policy-file-request/>")) { out.println("..."+EOF); // Policy file System.out.println(server.getInetAddress()+": Policy Request"); disconnect=true; System.out.println("Matched 2"); }else if(line.substring(0,3).equals("GET")||line.substring(0,4).equals("POST")){ out.println("HTTP/1.0 200 OK\nServer: VirtuaRoom v0.9\nContent-Type: text/html\n\n..."); // HTML status page disconnect=true; System.out.println("Matched 3"); } else { System.out.println(server.getInetAddress()+": Unknown command, client disconnected."); disconnect=true; System.out.println("Matched else"); } } server.close(); First of all, the client sends an "h" packet, and expects the same back (handshake). However, I want it to disconnect the client when an unrecognised packet is received. For some reason, it responds fine to the handshake and HTML status request, but the else clause is never executed when there's an unknown packet. Thanks

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  • TCP socket communication

    - by raven
    hello, I am creating a Chat in java. I have a method (onMouseRelease) inside an object that creates a tcp server and waits for a socket like this: ServerSocket server = new ServerSocket(port); Socket channel = server.accept(); Now I want to make a thread that will loop and read data from the socket, so that once the user on the other side sends me a string, I will extract the data from the socket (or is it called packet? Sorry, I am new to this) and update a textbox to add the additional string from the socket (or packet?). I have no idea how to READ (extract) the information from the socket(/packet) and then update it into a JTextArea which is called userOutput. And how to send a string to the other client, so that it will also could read the new data and update its JTextArea. From what I know, for a 2 sided TCP communication you need one computer to host a server and the other to connect (as a client) and once the connection is set the client can also receive new information from the socket. Is that true? and please tell me how. Any help is appreciated! I know this is a bit long but I have searched a lot and didn't understand it (I saw something like PrintWriter but failed to understand).

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  • Java: GatheringByteChannel advantages?

    - by Jason S
    I'm wondering when the GatheringByteChannel's write methods (taking in an array of ByteBuffers) have advantages over the "regular" WritableByteChannel write methods. I tried a test where I could use the regular vs. the gathering write method on a FileChannel, with approx 400KB/sec total in ByteBuffers of between 23-27 bytes in length in both cases. Gathering writes used an array of 64. The regular method used up approx 12% of my CPU, and the gathering method used up approx 16% of my CPU (worse than the regular method!) This tells me it's NOT useful to use gathering writes on a FileChannel around this range of operating parameters. Why would this be the case, and when would you ever use GatheringByteChannel? (on network I/O?) Relevant differences here: public void log(Queue<Packet> packets) throws IOException { if (this.gather) { int Nbuf = 64; ByteBuffer[] bbufs = new ByteBuffer[Nbuf]; int i = 0; Packet p; while ((p = packets.poll()) != null) { bbufs[i++] = p.getBuffer(); if (i == Nbuf) { this.fc.write(bbufs); i = 0; } } if (i > 0) { this.fc.write(bbufs, 0, i); } } else { Packet p; while ((p = packets.poll()) != null) { this.fc.write(p.getBuffer()); } } }

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  • OpenVPN Error : TLS Error: local/remote TLS keys are out of sync: [AF_INET]

    - by Lucidity
    Fist off thanks for reading this, I appreciate any and all suggestions. I am having some serious problems reconnecting to my OpenVPN client using Riseup.net's VPN. I have spent a few days banging my head against the wall in attempts to set this up on my iOS devices....but that is a whole other issue. I was however able to set it up on my Mac OS X specifically on my Windows Vista 32 bit BootCamp VM with relatively little trouble. To originally connect I only had to modify the recommended Config file very slightly (Config file included at the end of this post): - I had to enter the code directly into my config file - And change "dev tap" to "dev tun" So I was connected. (Note - I did test to ensure the VPN was actually working after I originally connected, it was. Also verified the .pem file (inserted as the coding in my config file) for authenticity). I left the VPN running. My computer went to sleep. Today I went to use the internet expecting (possibly incorrectly - I am now unsure if I was wrong to leave it running) to still be connected to the VPN. However I saw immediately I was not. I went to reconnect. And was (am) unable to. My logs after attempting to connect (and getting a connection failed dialog box) show everything working as it should (as far as I can tell) until the end where I get the following lines: Mon Sep 23 21:07:49 2013 us=276809 Initialization Sequence Completed Mon Sep 23 21:07:49 2013 us=276809 MANAGEMENT: >STATE:1379995669,CONNECTED,SUCCESS, OMITTED Mon Sep 23 21:22:50 2013 us=390350 Authenticate/Decrypt packet error: packet HMAC authentication failed Mon Sep 23 21:23:39 2013 us=862180 TLS Error: local/remote TLS keys are out of sync: [AF_INET] VPN IP OMITTED [2] Mon Sep 23 21:23:57 2013 us=395183 Authenticate/Decrypt packet error: packet HMAC authentication failed Mon Sep 23 22:07:41 2013 us=296898 TLS: soft reset sec=0 bytes=513834601/0 pkts=708032/0 Mon Sep 23 22:07:41 2013 us=671299 VERIFY OK: depth=1, C=US, O=Riseup Networks, L=Seattle, ST=WA, CN=Riseup Networks, [email protected] Mon Sep 23 22:07:41 2013 us=671299 VERIFY OK: depth=0, C=US, O=Riseup Networks, L=Seattle, ST=WA, CN=vpn.riseup.net Mon Sep 23 22:07:46 2013 us=772508 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Mon Sep 23 22:07:46 2013 us=772508 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Mon Sep 23 22:07:46 2013 us=772508 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Mon Sep 23 22:07:46 2013 us=772508 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Mon Sep 23 22:07:46 2013 us=772508 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 2048 bit RSA So I have searched for a solution online and I have included what I have attempted below, however I fear (know) I am not knowledgeable enough in this area to fix this myself. I apologize in advance for my ignorance. I do tech support for a living, but not this kind of tech support unfortunately. Other notes and troubleshooting done - - Windows Firewall is disabled completely, as well as other Anti-virus programs - Tor is disabled completely - No Proxies running - Time is correct in all locations - Router Firmware is up to date - Able to connect to the internet and as far as I can tell all necessary ports are open. - No settings have been altered since I was able to connect successfully. - Ethernet as well as wifi connections attempted, resulted in same error. Also tried adding the following lines to my config file (without success or change in error): persist-key persist-tun proto tcp (after reading that this error generally occurs on UDP connections, and is extremely rare on TCP) resolv-retry infinite (thinking the connection may have timed out since the issues occurred after leaving VPN connected during about 10 hrs of computer in sleep mode) All attempts resulted in exact same error code included at the top of this post. The original suggestions I found online stated - (regarding the TLS Error) - This error should resolve itself within 60 seconds, or if not quit wait 120 seconds and try again. (Which isnt the case here...) (regarding the Out of Sync" error) - If you continue to get "out of sync" errors and the link does not come up, then it means that something is probably wrong with your config file. You must use either ping and ping-restart on both sides of the connection, or keepalive on the server side of a client/server connection, in order to gracefully recover from "local/remote TLS keys are out of sync" errors. I wouldn't be surprised if my config file is lacking, or not correct. However I can confirm I followed the instructions to a tee. And was able to connect originally (and have not modified my settings or config file since I was able to connect to when the error began occurring). I have a very simple config file: client dev tun tun-mtu 1500 remote vpn.riseup.net auth-user-pass ca RiseupCA.pem redirect-gateway verb 4 <ca> -----BEGIN CERTIFICATE----- [OMITTED] -----END CERTIFICATE----- </ca> I would really appreciate any help or suggestions. I am at a total loss here, I know I'm asking a lot here. Though I am a new user on this site I help others on many forums including Microsoft's support community and especially Apple's support communities, so I will definitely pass on anything I learn here to help others. Thanks so so so much in advance for reading this.

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