The Transport Control Protocol (TCP) is a low-level part of the protocol stack used by the Internet. It sits directly above the IP layer and is responsible for making sure that dropped packets are resent.

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425 views

iptables string not dropping packet from tcp streams while using conntrack and string

I'm facing an unusual issue where specific TCP steams are not getting dropped by iptables; instead it's like iptables is just removing those specific packets. We're getting the following traffic: ...
2
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1answer
117 views

Browser fails to reach any host on Solaris 8

I'm running Solaris 8 on a Sun Ultra 2 connected to a Verizon router. nslookup seems to work (it finds google.com) but the existing browser (Netscape 4.76 - yes - it's very old) fails to reach any web ...
0
votes
1answer
342 views

Read and parse XML input via TCP [closed]

I'm setting up something where I'll need to be able to setup a service that accepts input on a TCP port and then parses the XML provided and extracts the necessary data, then posts that to Google's ...
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0answers
84 views

configure allowed_tcp_congestion_control via config files in linux kernel

I am trying to come up with a custom set of TCP congestion control variants as part of the tcp_allowed_congestion_control. I do have multiple variants on my tcp_available_congestion_control list but ...
3
votes
3answers
612 views

Transfer a TCP connection from one Linux box to another behind NAT?

While experiencing an extremely slow download rate on one of my HTTP connections, I thought it'd be nice if I could just transfer the connection from my PC to an energy-saving home server that shares ...
3
votes
2answers
3k views

Is there a faster interface for info from /proc/net/tcp?

Given a linux TCP socket's inode (obtained via /proc/<pid>/fd), is there a faster way to look up the information that I can get from /proc/net/tcp about this socket? I have written a ...
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2answers
84 views

Is Port 13330 a standard-port?

I saw some programs using the port 13330. What is the meaning of this port? Is this port used by a special program?
3
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2answers
1k views

200ms latency between TCP send and tcpdump only with large messages

In our REHL server, latency between application send and tcpdump log is always very large for large messages, about 200 milliseconds (see below 697572-488690=208882 microseconds), whereas latency for ...
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3answers
4k views

rsh runs perfectly in normal user but not in root, very strange, why?

When I run command, rsh localhost pwd as a root It shows below output. connect to address 127.0.0.1 port 544: Connection refused Trying krb4 rsh... connect to address 127.0.0.1 port 544: Connection ...
3
votes
2answers
7k views

Checking if I can reach some ports from my computer

Is there a terminal command or something on OSX that I can use to test if I can reach some ports on a remote server? I know these ports are reachable on that server, because I can access them from ...
0
votes
1answer
134 views

What are the other congestion control algorithms specially designed for lossy Wireless Networks like LTE and WiMax?

I am trying different congestion control algorithms for getting maximum throughput and minimum delay across my setup for TCP flow.Please suggest other available algorithms apart from Veno, ...
2
votes
3answers
2k views

Linux Shell Script - Send command over TCP to Sharp Aquos

I'm writing a shell script that needs to send an 8 character string terminated with a x0d to a Sharp Aquos TV. An example is 'POWR1 \x0d' (POWR1 followed by three spaces and LF) The documentation ...
0
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3answers
695 views

How to send an email to myself on the same local machine (tcp port 25)

Does anyone know how to sent email to myself? I am trying to generate TCP traffic on port 25.
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vote
1answer
793 views

How to display TCP handshake in Linux [closed]

Hi is there a way to display TCP handshake in Linux? Like for example this WIKI - TCP handshake Not exactly like the illustration but at least it would show client has sent SYN, ACK, FIN etc and the ...
3
votes
1answer
919 views

How to run Different congestion control algorithms in FEDORA 17 ..?

Earlier versions of Fedora has different loadable kernel modules which includes diffrent congestion control algorithms etc at (/lib/modules/"kernel-name"/kernel/ipv4).These are present in the form of ...
0
votes
2answers
582 views

Why my Http Proxy doesn't reply [SYN,ACK] after received a [SYN] packet from the client?

I have a http proxy running on Linux (RHEL 5.5), intermittently it doesn't reply [SYN,ACK] packet after received a [SYN] packet from the client. This issue can be recovered by restarting the proxy. I ...
2
votes
1answer
2k views

Why can't I use strace with rsh?

If I run rsh, it works, but prints some strange “Connection refused” messages at the beginning: $ rsh localhost pwd connect to address 127.0.0.1 port 544: Connection refused Trying krb4 rsh... ...
26
votes
1answer
802 views

Why does it take up to several minutes to clean a listening TCP port after a program dies?

If I kill a program that is listening on a TCP port, it takes up to several minutes until the port is reclaimed by the system and usable again. I've seen several Q/A mentioning this phenomenon, but ...
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vote
2answers
2k views

Why TCP TIME-WAIT State is present at both ends after a connection termination?

I am reading how the TCP states work and especially the connection termination part. All of the books or online material I read, shows that for the termination procedure these states are followed ...
9
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2answers
20k views

Getting current TCP connection count on a system

Instead of doing wc -l /proc/net/tcp, is there a faster way of doing it? I just need a total count of tcp connections.
1
vote
1answer
1k views

Default value for SO_RCVTIMEO option on Solaris

Is there any way to find out what is the default value set for option SO_RCVTIMEO on Solaris 10? If there is a way to find out how would one go about changing it? P.S. I am aware of ability of ...
2
votes
2answers
1k views

Port forwarding and masquerading

What is the relationship between port-forwarding and masquerading? If server A is configured to masquerade its clients, and client B accesses the Internet through server A, then since client B is ...
5
votes
2answers
125 views

Is it more dangerous to connect to the net as root?

If I make some kind of tcp connection to the net as root, is that less safe then making the same tcp connection as a normal user? I have been suspecting for a while that by making a connection as ...
2
votes
1answer
514 views

Running a local port scan and found open ports but, don't know what they're used for?

I wrote a very basic python script to port scan my system. I'm running linux-mint lisa: open_ports = [] for port in xrange(65536): conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM) ...
3
votes
3answers
1k views

What process is sending TCP SYNs on Solaris 10?

Some process on my Solaris 10 machine is sending TCP SYNs to a remote machine. The remote machine never responds, so the connection is not established. How do I find out what process is initiating ...
3
votes
2answers
733 views

Meaning of log entries from an iptables configuration

My router has Linux as its OS. The system log has a lot of rows about iptable and klogd that I don't understand, could someone explain them to me? The iptables setup: iptables -t nat -A PREROUTING ...
2
votes
1answer
219 views

How do I ensure outbound TCP/IP traffic always uses a VPN, even when using Wifi?

I'd like to ensure that my VPN is started and running, before any TCP traffic from any of my background services send or receive data. How can I guarantee that this is the case? How do I handle ...
2
votes
1answer
4k views

Adjusting rsync TCP timeout

I'm using rsync in my own C++ program by issueing the command system("rsync -rauzvq root@host:/folder"); I use this for keeping multiple systems in sync. Now I have the problem that when a remote ...
3
votes
1answer
1k views

Closing socket connection on running console application

I am testing a chat bot and want to gracefully handle for times when the chat server isn't running so it can come back up when the service is available again. I have the programming handled. My ...
2
votes
1answer
1k views

Memory ussage for TCP or named pipe message buffers?

I have a group of programs that I was stress testing today. I drastically shot up the input load to the program and it worked at first, but I had an apparent memory leak sucking up memory. The only ...
4
votes
2answers
4k views

What is the relation between DISPLAY :1.0 and port 5901

When I start a new X server using vncserver I can connect it using port 5901. From, say, a terminal, I can also do a: export DISPLAY=:1.0 xterm (it's just an example) And I get an xterm on the ...
3
votes
2answers
185 views

How to detect out-bound port from PID

I have several applications that run on random ports. How would I take the pid or the file location and find which port it is running on? Example of desired output: www-data/apache = 80 ...
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votes
4answers
16k views

testing services/open ports with telnet?

I often see that folks test ports this way: //shell telnet ip-address 80 telnet ip-address 25 AFAIK telnet was the old way of getting onto some remote box - right? or so I thought... Why exactly ...
0
votes
1answer
837 views

Can't connect remotely to server running redhat (ec2)

I created a RedHat 6.1 VM with EC2. Logged in as root, I installed (unzipped) JDK1.7 in /root/bin/jdk1.7.0 and installed (unzipped) GlassFish 3.1.1 in /root/bin/glassfish3. I set JAVA_HOME and ...
4
votes
2answers
1k views

How to listen to all ports (UDP and TCP) or make them all appear open in Debian

I got an external Debian server. The problem is that my university campus doesn't allow connections to go outside when the port is different than TCP port 22, 80, 443, or UDP port 123. I tested them ...
1
vote
1answer
544 views

php mail not working in rhel server?

I have installed roundcube mail and when it tried to use installer which uses php mail it is loading for 5 to 10 minutes and then telling me 'ok' but no mail comes to me. smtp_port is 25 host is ...
3
votes
1answer
404 views

Route incoming network requests for a given port to different applications

I have an application that listens for connections on a port, but I occasionally take it down for updates and the like. I'd like a way to configure the system such that if that program is running, ...
25
votes
1answer
8k views

Why doesn't Linux use the IANA Ephemeral port range?

According to Wikipedia The Internet Assigned Numbers Authority (IANA) suggests the range 49152 to 65535 for dynamic or private ports. Many Linux kernels use the port range 32768 to 61000. Even ...
1
vote
3answers
2k views

Books/Resources which explain TCP/IP kernel implementation [closed]

I only know about: 1) Internetworking with TCP/IP: Vol.II, Design, Implementation, and Internals 2) TCP/IP Illustrated, Vol. 2: The Implementation but these are quite dated. I am particularly ...
4
votes
3answers
407 views

How to measure the time when a packet arrives?

When the packet arrives the NIC generates an interrupt and the kernel then takes over. I want to measure the time at which a packet of a particular TCP flow arrives. How do I do this in Linux? This ...
2
votes
1answer
246 views

Why does this simple Perl client not work?

I am fairly new to IPC with sockets and expect this issue is a simple one to resolve. I'm trying to understand why I cannot get this example script from perldoc perlipc to run on my Ubuntu setup: ...
5
votes
2answers
14k views

Linux Networking routing to virtual ip addresses from a different subnet

New to linux networking, had a question about routing to virtual ip addresses from a different subnet. I have three servers (they can all ping each other): A 10.10.51.182 (connected to router ...
3
votes
1answer
6k views

Kill TIME_WAIT sockets immediately?

Is there anyway to kill those TIME_WAIT sockets immediately ? e.g output of netstat: tcp 0 0 127.0.0.1:8080 127.0.0.1:41500 TIME_WAIT - tcp 0 ...
4
votes
3answers
2k views

IPTables and transparent proxies

I have set up a local, transparent TCP proxy on localhost. I want to redirect ALL TCP traffic to this proxy, so it can handle it and nothing "leaks out," circumventing the proxy. I need to use ...
10
votes
3answers
8k views

Using in/out named pipes for a TCP connection

I've been fiddling with getting this to work for a while now, so I suspect some sort of fundamental misunderstanding about how pipes work is the root cause of my troubles. My goal is to initiate a ...
3
votes
3answers
1k views

How can I read lines at a fixed speed?

I need to read a large log file and send it over a local network using (netbsd) netcat between two VMs on the same host workstation. I know that netcat has an interval, but as far as I can tell, the ...
7
votes
1answer
3k views

/dev/tcp not present in Linux

I am porting C/pro*c code from UNIX to Linux. The code is: #define __NFDBIT (8 * sizeof(unsigned long)) #define __FD_SETSIZ 1024 #define __FDSET_LONG (__FD_SETSIZ/__NFDBIT) typedef struct ...
3
votes
1answer
510 views

User associated with a socket

I use ss -p to see TCP sockets information. But process info are not printed for some sockets. Below: $ ss -p4 State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 0 ...
6
votes
3answers
3k views

Faster alternatives to lsof

I want to extract the process id of a certain process in order to shut it down. The process is a local web server using a certain port (localhost:3000), and I am currently doing it like this to ...
1
vote
1answer
455 views

How to limit all tcp traffic to the network interface the session was initiated on?

I have an embedded linux system with two network interfaces (lan0, wlan0) that are configured to the same subnet. A server on this system accepts tcp connections on both interfaces. How I can assure ...