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  • TCP Server to push data to a Web Browser

    - by isurulucky
    Hi, I have a TCP server, which is connected to a web page via a Web browser. It is easy to send a request to the TCP server by the web page via the Web Browser, but is there a way that TCP server can push data to the web browser, without waiting for a request from browser side?? My initial idea was that this is impossible, since a browser is stateless. But I was told there are ways to do that... Any ideas? Thank You!!

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  • How Proxy server works with tcp/http connections?

    - by Vivek
    Since I am a beginner in the world of internet/networking, I always mess up with these kinds of doubts in my head while programming ;) .. My doubts are, While working behind a proxy, how my requests and responses work? Means my request headers and data will first reach to Proxy server- then proxy server sends it(same headers and data) to corresponding server. And server responses to it with a response header and body to the proxy server-then proxy server sends it to my computer. Wright? While using websockets we are upgrading our http connection to tcp. At this time what is happening @ Proxy server? Does the proxyserver also upgrades its connection to plain TCP? After opening such TCP connections, does the proxy server able to track/log those socket messsages? And most importantly, Is the proxy server transparent or acting like an original server infront of a client? Thanks for any answers or helpful links in advance.

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  • Cannot connect to MySQL over TCP locally - Connection Timeout - Ubuntu 9.04

    - by gav
    I am running Ubuntu and am ultimately trying to connect Tomcat to my MySQL database using JDBC. It has worked previously but after a reboot the instance now fails to connect. Both Tomcat 6 and MySQL 5.0.75 are on the same machine Connection string: jdbc:mysql:///localhost:3306 I can connect to MySQL on the command line using the mysql command The my.cnf file is pretty standard (Available on request) has bind address: 127.0.0.1 I cannot Telnet to the MySQL port despite netstat saying MySQL is listening I have one IpTables rule to forward 80 - 8080 and no firewall I'm aware of. I'm pretty new to this and I'm not sure what else to test. I don't know whether I should be looking in etc/interfaces and if I did what to look for. It's weird because it used to work but after a reboot it's down so I must have changed something.... :). I realise a timeout indicates the server is not responding and I assume it's because the request isn't actually getting through. I installed MySQL via apt-get and Tomcat manually. MySqld processes root@88:/var/log/mysql# ps -ef | grep mysqld root 21753 1 0 May27 ? 00:00:00 /bin/sh /usr/bin/mysqld_safe mysql 21792 21753 0 May27 ? 00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock root 21793 21753 0 May27 ? 00:00:00 logger -p daemon.err -t mysqld_safe -i -t mysqld root 21888 13676 0 11:23 pts/1 00:00:00 grep mysqld Netstat root@88:/var/log/mysql# netstat -lnp | grep mysql tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 21792/mysqld unix 2 [ ACC ] STREAM LISTENING 1926205077 21792/mysqld /var/run/mysqld/mysqld.sock Toy Connection Class root@88:~# cat TestConnect/TestConnection.java import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; public class TestConnection { public static void main(String args[]) throws Exception { Connection con = null; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); System.out.println("Got driver"); con = DriverManager.getConnection( "jdbc:mysql:///localhost:3306", "uname", "pass"); System.out.println("Got connection"); if(!con.isClosed()) System.out.println("Successfully connected to " + "MySQL server using TCP/IP..."); } finally { if(con != null) con.close(); } } } Toy Connection Class Output Note: This is the same error I get from Tomcat. root@88:~/TestConnect# java -cp mysql-connector-java-5.1.12-bin.jar:. TestConnection Got driver Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet sent successfully to the server was 1 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122) at TestConnection.main(TestConnection.java:14) Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122) at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181) ... 12 more Caused by: java.net.ConnectException: Connection timed out at java.net.PlainSocketImpl.socketConnect(Native Method) ... 13 more Telnet Output root@88:~/TestConnect# telnet localhost 3306 Trying 127.0.0.1... telnet: Unable to connect to remote host: Connection timed out

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  • Cannot connect to MySQL Server on RHEL 5.7

    - by Jeffrey Wong
    I have a standard MySQL Server running on Red hat 5.7. I have edited /etc/my.cnf to specify the bind address as my server's public IP address. [mysqld] datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock user=mysql # Default to using old password format for compatibility with mysql 3.x # clients (those using the mysqlclient10 compatibility package). old_passwords=1 # Disabling symbolic-links is recommended to prevent assorted security risks ; # to do so, uncomment this line: # symbolic-links=0 [mysqld_safe] log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid bind-address=171.67.88.25 port=3306 And I have also restarted my firewall sudo /sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 3306 -j ACCEPT /sbin/service iptables save The network administrator has already opened port 3306 for this box. When connecting from a remote computer (running Ubuntu 10.10, server is running RHEL 5.7), I issue mysql -u jeffrey -p --host=171.67.88.25 --port=3306 --socket=/var/lib/mysql/mysql.sock but receive a ERROR 2003 (HY000): Can't connect to MySQL server on '171.67.88.25' (113). I've noticed that the socket file /var/lib/mysql/mysql.sock is blank. Should this be the case? UPDATE The result of netstat -an | grep 3306 tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN Result of sudo netstat -tulpen Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name tcp 0 0 127.0.0.1:2208 0.0.0.0:* LISTEN 0 7602 3168/hpiod tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 27 7827 3298/mysqld tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 0 5110 2802/portmap tcp 0 0 0.0.0.0:8787 0.0.0.0:* LISTEN 0 8431 3326/rserver tcp 0 0 0.0.0.0:915 0.0.0.0:* LISTEN 0 5312 2853/rpc.statd tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 0 7655 3188/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 0 7688 3199/cupsd tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 0 8025 3362/sendmail: acce tcp 0 0 127.0.0.1:2207 0.0.0.0:* LISTEN 0 7620 3173/python udp 0 0 0.0.0.0:909 0.0.0.0:* 0 5300 2853/rpc.statd udp 0 0 0.0.0.0:912 0.0.0.0:* 0 5309 2853/rpc.statd udp 0 0 0.0.0.0:68 0.0.0.0:* 0 4800 2598/dhclient udp 0 0 0.0.0.0:36177 0.0.0.0:* 70 8314 3476/avahi-daemon: udp 0 0 0.0.0.0:5353 0.0.0.0:* 70 8313 3476/avahi-daemon: udp 0 0 0.0.0.0:111 0.0.0.0:* 0 5109 2802/portmap udp 0 0 0.0.0.0:631 0.0.0.0:* 0 7691 3199/cupsd Result of sudo /sbin/iptables -L -v -n Chain INPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 6373 2110K RH-Firewall-1-INPUT all -- * * 0.0.0.0/0 0.0.0.0/0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 0 0 RH-Firewall-1-INPUT all -- * * 0.0.0.0/0 0.0.0.0/0 Chain OUTPUT (policy ACCEPT 1241 packets, 932K bytes) pkts bytes target prot opt in out source destination Chain RH-Firewall-1-INPUT (2 references) pkts bytes target prot opt in out source destination 572 861K ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 1 28 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmp type 255 0 0 ACCEPT esp -- * * 0.0.0.0/0 0.0.0.0/0 0 0 ACCEPT ah -- * * 0.0.0.0/0 0.0.0.0/0 46 6457 ACCEPT udp -- * * 0.0.0.0/0 224.0.0.251 udp dpt:5353 0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:631 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:631 782 157K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 2 120 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:443 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:23 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80 4970 1086K REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited Result of nmap -P0 -p3306 171.67.88.25 Host is up (0.027s latency). PORT STATE SERVICE 3306/tcp filtered mysql Nmap done: 1 IP address (1 host up) scanned in 0.09 seconds Solution When everything else fails, go GUI! system-config-securitylevel and add port 3306. All done!

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  • How Hacker Can Access VPS CentOS 6 content?

    - by user2118559
    Just want to understand. Please, correct mistakes and write advices Hacker can access to VPS: 1. Through (using) console terminal, for example, using PuTTY. To access, hacker need to know port number, username and password. Port number hacker can know scanning open ports and try to login. The only way to login as I understand need to know username and password. To block (make more difficult) port scanning, need to use iptables configure /etc/sysconfig/iptables. I followed this https://www.digitalocean.com/community/articles/how-to-setup-a-basic-ip-tables-configuration-on-centos-6 tutorial and got *nat :PREROUTING ACCEPT [87:4524] :POSTROUTING ACCEPT [77:4713] :OUTPUT ACCEPT [77:4713] COMMIT *mangle :PREROUTING ACCEPT [2358:200388] :INPUT ACCEPT [2358:200388] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [2638:477779] :POSTROUTING ACCEPT [2638:477779] COMMIT *filter :INPUT DROP [1:40] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [339:56132] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP -A INPUT -p tcp -m tcp ! --tcp-flags FIN,SYN,RST,ACK SYN -m state --state NEW -j DROP -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,SYN,RST,PSH,ACK,URG -j DROP -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT -A INPUT -p tcp -m tcp --dport 110 -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -s 11.111.11.111/32 -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m tcp --dport 21 -j ACCEPT -A INPUT -s 11.111.11.111/32 -p tcp -m tcp --dport 21 -j ACCEPT COMMIT Regarding ports that need to be opened. If does not use ssl, then seems must leave open port 80 for website. Then for ssh (default 22) and for ftp (default 21). And set ip address, from which can connect. So if hacker uses other ip address, he can not access even knowing username and password? Regarding emails not sure. If I send email, using Gmail (Send mail as: (Use Gmail to send from your other email addresses)), then port 25 not necessary. For incoming emails at dynadot.com I use Email Forwarding. Does it mean that emails “does not arrive to VPS” (before arriving to VPS, emails are forwarded, for example to Gmail)? If emails does not arrive to VPS, then seems port 110 also not necessary. If use only ssl, must open port 443 and close port 80. Do not understand regarding port 3306 In PuTTY with /bin/netstat -lnp see Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 992/mysqld As understand it is for mysql. But does not remember that I have opened such port (may be when installed mysql, the port is opened automatically?). Mysql is installed on the same server, where all other content. Need to understand regarding port 3306 2. Also hacker may be able access console terminal through VPS hosting provider Control Panel (serial console emergency access). As understand only using console terminal (PuTTY, etc.) can make “global” changes (changes that can not modify with ftp). 3. Hacker can access to my VPS exploiting some hole in my php code and uploading, for example, Trojan. Unfortunately, faced situation that VPS was hacked. As understand it was because I used ZPanel. On VPS ( \etc\zpanel\panel\bin) ) found one php file, that was identified as Trojan by some virus scanners (at virustotal.com). Experimented with the file on local computer (wamp). And appears that hacker can see all content of VPS, rename, delete, upload etc. From my opinion, if in PuTTY use command like chattr +i /etc/php.ini then hacker could not be able to modify php.ini. Is there any other way to get into VPS?

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  • Linux, some packets are not being NAT

    - by user70932
    Hi, I'm trying to NAT HTTP traffic, I'm new to this and facing some issues. What i'm trying to do is NAT client HTTP requests to a webserver. CLIENT - NAT BOX - WEBSERVER When the client open the IP of the NAT BOX, the request should be pass to the web server. But I'm getting "HTTP request sent, awaiting response..." and then wait serveral minutes before the request is done. Looking at the tcpdump output, it looks like the first Syn packet on (10:48:54) is being NAT but not the second, third, fourth... ACK or PSH packets, and wait until (10:52:04) it starts NAT again on the ACK packet. The iptables command I'm using is: iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 \ -j DNAT --to-destination WEBSERVER I'm wondering what could have caused this behavior? Thanks alot. 10:48:54.907861 IP (tos 0x0, ttl 49, id 16395, offset 0, flags [DF], proto: TCP (6), length: 48) CLIENT.61736 > NATBOX.http: S, cksum 0x6019 (correct), 1589600740:1589600740(0) win 5840 <mss 1460,nop,wscale 8> 10:48:54.907874 IP (tos 0x0, ttl 48, id 16395, offset 0, flags [DF], proto: TCP (6), length: 48) CLIENT.61736 > WEBSERVER.http: S, cksum 0xb5d7 (correct), 1589600740:1589600740(0) win 5840 <mss 1460,nop,wscale 8> 10:48:55.102696 IP (tos 0x0, ttl 49, id 16397, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x2727 (correct), ack 2950613896 win 23 10:48:55.102963 IP (tos 0x0, ttl 49, id 16399, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:48:58.103078 IP (tos 0x0, ttl 49, id 16401, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:48:58.366344 IP (tos 0x0, ttl 49, id 16403, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x26af (correct), ack 1 win 23 10:49:04.103204 IP (tos 0x0, ttl 49, id 16405, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:49:04.363943 IP (tos 0x0, ttl 49, id 16407, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x26af (correct), ack 1 win 23 10:49:16.101583 IP (tos 0x0, ttl 49, id 16409, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:49:16.363475 IP (tos 0x0, ttl 49, id 16411, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x26af (correct), ack 1 win 23 10:49:40.100796 IP (tos 0x0, ttl 49, id 16413, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:49:40.563898 IP (tos 0x0, ttl 49, id 16415, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x26af (correct), ack 1 win 23 10:50:28.099396 IP (tos 0x0, ttl 49, id 16417, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:50:28.761678 IP (tos 0x0, ttl 49, id 16419, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x26af (correct), ack 1 win 23 10:52:04.093668 IP (tos 0x0, ttl 49, id 16421, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > NATBOX.http: P 0:120(120) ack 1 win 23 10:52:04.093678 IP (tos 0x0, ttl 48, id 16421, offset 0, flags [DF], proto: TCP (6), length: 160) CLIENT.61736 > WEBSERVER.http: P 1589600741:1589600861(120) ack 2950613896 win 23 10:52:04.291021 IP (tos 0x0, ttl 49, id 16423, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x25d3 (correct), ack 217 win 27 10:52:04.291028 IP (tos 0x0, ttl 48, id 16423, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > WEBSERVER.http: ., cksum 0x7b91 (correct), ack 217 win 27 10:52:04.300708 IP (tos 0x0, ttl 49, id 16425, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x253c (correct), ack 368 win 27 10:52:04.300714 IP (tos 0x0, ttl 48, id 16425, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > WEBSERVER.http: ., cksum 0x7afa (correct), ack 368 win 27 10:52:04.301417 IP (tos 0x0, ttl 49, id 16427, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: F, cksum 0x253b (correct), 120:120(0) ack 368 win 27 10:52:04.301438 IP (tos 0x0, ttl 48, id 16427, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > WEBSERVER.http: F, cksum 0x7af9 (correct), 120:120(0) ack 368 win 27 10:52:04.498875 IP (tos 0x0, ttl 49, id 16429, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > NATBOX.http: ., cksum 0x253a (correct), ack 369 win 27 10:52:04.498881 IP (tos 0x0, ttl 48, id 16429, offset 0, flags [DF], proto: TCP (6), length: 40) CLIENT.61736 > WEBSERVER.http: ., cksum 0x7af8 (correct), ack 369 win 27

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  • checksum in raw sockets and pcap [closed]

    - by hero
    i am using pcap library to sniff some packets, change their tcp data , and then inject my packet on the network. my question is: if i changed in the tcp data, should i recalculate the length field in the tcp header? should i also change the checksum? i read in a page on how to create raw sockets that if you set the tcp_checksum to 0, the kernel will automatically calculate it and fill it, is this true for windows machines also?

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  • Unable to connect to mail server via IMAP and roundcube

    - by mrhatter
    I am having trouble getting the final parts of my mail server up and working. I followed this tutorial to get everything set up on the mail server side. I have installed roundcube for webmail and configured it but it is saying "error connecting, connection refused" when attempting to connect to it using IMAP. This is thorough the "test imap" section of its installer. Also it is giving me an error message about perissions for it's log and temp folders but that's not as important as acutally getting mail to work. I have also tried connecting to the mail server using thunderbird however it cannot establish a connection either and I know my login information is correct. I know that the databases are working correctly based on the roundcube installer telling me that they have been "successfully initialized". Here are my firewall rules -A INPUT -i lo -j ACCEPT -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m tcp --dport 25 -j ACCEPT -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT -A INPUT -p tcp -m tcp --dport 465 -j ACCEPT -A INPUT -p tcp -m tcp --dport 487 -j ACCEPT -A OUTPUT -p tcp -m tcp --dport 993 -j ACCEPT -A INPUT -j DROP Which I set up in iptables. I have modified them from what I used in this tutorial I'm not sure what to try next. Any help would be wonderful! I am using Ubuntu 14.04 server, apache 2.4.7, roundcube 1.0.1, and the latest versions of dovecot and postfix. The email databases are contained in mysql. I am running this on a VPS server. UPDATE: I have changed from iptables to using ufw. I have run the following commands to set up a basic firewall with ufw. ufw default deny ufw allow ssh ufw allow http ufw allow https ufw allow imap ufw allow imaps ufw allow smtp I then used telnet to check all of the mail ports. But Port 993 isnt working even though ufw says both 993 and 993/tcp are open. What am I missing?

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  • LVS TCP connection timeouts - lingering connections

    - by Jon Topper
    I'm using keepalived to load-balance connections between a number of TCP servers. I don't expect it matters, but the service in this case is rabbitmq. I'm using NAT type balancing with weighted round-robin. A client connects to the server thus: [client]-----------[lvs]------------[real server] a b If a client connects to the LVS and remains idle, sending nothing on the socket, this eventually times out, according to timeouts set using ipvsadm --set. At this point, the connection marked 'a' above correctly disappears from the output of netstat -anp on the client, and from the output of ipvsadm -L -n -c on the lvs box. Connection 'b', however, remains ESTABLISHED according to netstat -anp on the real server box. Why is this? Can I force lvs to properly reset the connection to the real server?

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  • Effects of HTTP/TCP connection handshakes and server performance

    - by Blankman
    When running apache bench on the same server as the website like: ab -n 1000 -c 10 localhost:8080/ I am most probably not getting accurate results when compared to users hitting the server from various locations. I'm trying to understand how or rather why this will effect real world performance since a user in china will have different latency issues when compared to someone in the same state/country. Say my web server has a maximum thread limit of 100. Can someone explain in detail how end user latency can/will effect server performance. I'm assuming here that each request will be computed equally at say 10ms. What I'm not understand is how external factors can effect overal server performance, specifically internet connections (location, or even device like mobile) and http/tcp handshakes etc.

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  • Tunnel only one program (UDP & TCP) through another server

    - by user136036
    I have a windows machine at home and a server with debian installed. I want to tunnel the UDP traffic from one (any only this) program on my windows machine through my server. For tcp traffic this was easy using putty as a socks5 proxy and then connecting via ssh to my server - but this does not seem to work for UDP. Then I setup dante as a socks5 proxy but it seems to create a new instance/thread per connection which leads to a huge ram usage for my server, so this was no option either. So most people recommend openvpn, so my question: Can I use openvpn to just tunnel this one program through my server? Is there a way to maybe create a local socks5 proxy on my windows machine and set it as a proxy in my program and only this proxy then will use openvpn? Thank you for your ideas

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  • MTU, DSL router and stalling TCP

    - by user38843
    I am discovering stalling TCP connection problem. The problem arises when I try to scp stuff from remote system from my home network. My home network is connected to internet via PPPoE (ADSL+) and everything works perfectly once working from my home network. The ADSL router has MTU set to 1492 but with that setting the scp from remote system does not work - stalling! When I change the MTU on my router to 1500 the that scp works perfectly but internet accesses from my home network is very slow to most of the www sites - even local ones. Just wondering where the problem exists - my ISP blocking ICMP, etc? Thanks!

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  • LVS TCP connection timeouts - lingering connections

    - by Jon Topper
    I'm using keepalived to load-balance connections between a number of TCP servers. I don't expect it matters, but the service in this case is rabbitmq. I'm using NAT type balancing with weighted round-robin. A client connects to the server thus: [client]-----------[lvs]------------[real server] a b If a client connects to the LVS and remains idle, sending nothing on the socket, this eventually times out, according to timeouts set using ipvsadm --set. At this point, the connection marked 'a' above correctly disappears from the output of netstat -anp on the client, and from the output of ipvsadm -L -n -c on the lvs box. Connection 'b', however, remains ESTABLISHED according to netstat -anp on the real server box. Why is this? Can I force lvs to properly reset the connection to the real server?

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  • Where is the actual content in a TCP segment

    - by packetloss
    When I email something or download a program, or do anything else over a network, where in the segment is the actual content? If I am emailing a 20KB word document, and the maximum data field size in a segment is 1500 bytes, does that mean it takes about 14 segments to mail my document wherever it is going? I get, I think, the OSI model and I have a decent grasp of the IP protocol. I think I understand the concept of header wrapping of each successive layer in the protocol stack. What I can't get a definitive answer to is where does the actual content go in a TCP segment? Is that the datagram? Maybe the fact I am asking proves I have no clue... Many thanks.

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  • Anyone else being hit by traffic on TCP port 11370

    - by Jakub
    I've been watching my logs (Ubuntu 9.10 server) and dunno about any of you but I am getting a ton of traffic from sources like Russia, Romania, etc.. on port 11370 (my iptables are logndrop'ing it. But was just curious). Some googling revealed this info: http://www.keysigning.org/sks/ -which seems to use port 11370 & 11371 Could that be the service they are scanning for (i don't run it)? ICS shows this: https://isc.incidents.org/port.html?port=11370 Just curious what you guys think and if anyone has seen this before? If need be I can post my log on here, but its just a dropped log of TCP port 11370 from various IPs. Thought it was strange as thats the ONLY Port I seem to repeatedly be hit on (from logs). I'm running on a Linode (VPS) if that matters to annyone.

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  • Accessing Windows from Linux/Mac by name using TCP/IP

    - by stevekuo
    What are some solutions to access Windows by its computer name from Linux and Mac using TCP/IP. That is, from terminal I want to be able to ping my Windows PCs using its host name. My setup is: Various machines running Ubuntu, Windows XP and OS X. Networked using a consumer grade wireless router which provides DHCP. The only DNS is the ISP's, which resolves Internet names and not local host names. The Windows machines can ping each other by name. The Ubuntu and OS X machines can only ping Windows by IP address (name doesn't work).

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  • TCP/IP performance tuning under KVM/Qemu

    - by vpetersson
    With more and more companies switching to public cloud services, I'm curious what you guys' thoughts are on TCP/IP tuning in the cloud. Is it worth bothering with? Given that you don't have access to the host-server, you're somewhat limited I presume Let's say for the sake of the argument that you're running three MongoDB-servers in a replica-set on FreeBSD or Linux that all sync over an internal network. I'd also be curious if anyone made any actual performance benchmarks to back up their arguments. I benchmarked the various network drivers available for KVM/Qemu here, but I'm curious what the gurus here suggest to tune further. I started playing around a bit with the tuning-recommendations as suggested over here, but interestingly enough I saw a decrease in performance, rather than an increase, but perhaps I didn't fully understand the tweaks. Update: I did a few more benchmarks and posted the result here. Unfortunately the result wasn't really what I expected.

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  • Remove Windows 7's limitation on number of concurrent tcp connections (http web requests)

    - by Ghita
    I have an application that tries to open as many http requests as possible (in order to stress test a proxy implementation) It seems to me that Win7 (SP1) may have a limitation on number of concurrent opened connection (it may be the so called half-open state if I'm not wrong). Is there something I can do for client ? and also I test using a vista PC that acts as a proxy server. It would be great if I could configure it to sustain at least 50 new connections initiated / second on client side and many more on server. I made the modification according to this technet article by setting TcpNumConnections = 150 but it doesn't make a difference. I still only see about 20 tcp sockets associated with my http client by using tcpview.

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  • Why are people trying to connect to me network on TCP port 445?

    - by Solignis
    I was playing with my new syslog server and had my m0n0wall firewall logs forwarded as a test, I noticed a bunch of recent firewall log entries that say that it blocked other WAN IPs from my ISP (I checked) from connecting to me on TCP port 445. Why would a random computer be trying to connect to me on a port apperently used for Windows SMB shares? Just internet garbage? A port scan? I am just curious. here is what I am seeing Mar 15 23:38:41 gateway/gateway ipmon[121]: 23:38:40.614422 fxp0 @0:19 b 98.82.198.238,60653 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN broadcast Mar 15 23:38:42 gateway/gateway ipmon[121]: 23:38:41.665571 fxp0 @0:19 b 98.82.198.238,60665 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN Mar 15 23:38:43 gateway/gateway ipmon[121]: 23:38:43.165622 fxp0 @0:19 b 98.82.198.238,60670 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN broadcast Mar 15 23:38:44 gateway/gateway ipmon[121]: 23:38:43.614524 fxp0 @0:19 b 98.82.198.238,60653 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN broadcast Mar 15 23:38:44 gateway/gateway ipmon[121]: 23:38:43.808856 fxp0 @0:19 b 98.82.198.238,60665 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN Mar 15 23:38:44 gateway/gateway ipmon[121]: 23:38:43.836313 fxp0 @0:19 b 98.82.198.238,60670 -> 98.103.xxx,xxx,445 PR tcp len 20 48 -S IN broadcast Mar 15 23:38:48 gateway/gateway ipmon[121]: 23:38:48.305633 fxp0 @0:19 b 98.103.22.25 -> 98.103.xxx.xxx PR icmp len 20 92 icmp echo/0 IN broadcast Mar 15 23:38:48 gateway/gateway ipmon[121]: 23:38:48.490778 fxp0 @0:19 b 98.103.22.25 -> 98.103.xxx.xxx PR icmp len 20 92 icmp echo/0 IN Mar 15 23:38:48 gateway/gateway ipmon[121]: 23:38:48.550230 fxp0 @0:19 b 98.103.22.25 -> 98.103.xxx.xxx PR icmp len 20 92 icmp echo/0 IN broadcast Mar 15 23:43:33 gateway/gateway ipmon[121]: 23:43:33.185836 fxp0 @0:19 b 98.86.34.225,64060 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN broadcast Mar 15 23:43:34 gateway/gateway ipmon[121]: 23:43:33.405137 fxp0 @0:19 b 98.86.34.225,64081 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN Mar 15 23:43:34 gateway/gateway ipmon[121]: 23:43:33.454384 fxp0 @0:19 b 98.86.34.225,64089 -> 98.103.xxx.xxx,445 PR tcp len 20 48 -S IN broadcast I blacked out part of my IP address for my own safety.

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  • TCP/IP over SSL and silverlight

    - by rahulchandran
    I want to write a silverlight page which connects to a tcp/ip server. The server is layering ssl as well. The problem is I don't see a SSLStream in Silverlight. Is this doable (I need the tcp/ip because this page will constantly get events from the server and no I don't want to poll, in fact I can't the server is third party) Thanks

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  • What's the difference between using ProtocolType.IP and ProtocolType.Tcp

    - by Sekhat
    I've just answered problem with sockets in c# where in my example code I initializing my socket using ProtocolType.IP as this is what I've always used in my own code, and it has never caused me problems. But I see many examples specifying ProtocolType.Tcp. I guess, what I'm asking is, by using ProtocolType.IP instead of ProtocolType.Tcp is anything being performed differently under the hood that I should be aware of?

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  • tcptrack shows SYN_SENT connections, does that mean the SYN package reached the server?

    - by xpu
    our server suffered a serious connection timeout problem, so we track tcp connection with tcptrack we found out that, if the client started to connect to the server, tcptrack shows the connection, but in SYN_SENT status, and netstat -nat shows nothing. (tcptrack & netstat all runs on the server) does this mean the syn request reached the server? and no syn/ack was sent back? why the tcptrack could report this connection but netstat could not? what could be the problem that a general apache could not establish a connection with the client? i did a bench test using ab in the same intranet, to the specified NIC, it handled 10000 concurrent connection and 400000 requests ok ps: this doesn't happen every time, but did happened a lot pps: is there any good tools to trace where the tcp connection was lost?

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  • Is it possible to load balance requests from a single source?

    - by Shawn
    In our application, Server A establishes a TCP connection with Server B, then it sends a large amount of requests to Server B over the TCP connection. The request message is XML-based. Server B needs to respond within a very short period, and it takes time to process the requests. So we hope a load balancer can be introduced and we can expedite the processing by using multiple Server B's. This is not a web application. I did some research but failed to find a similar application of load balancer. Can anyone tell me if there's a load balancer can help in our application?

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