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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Port 80 refused by Linux (Ubunt 12.04)

I am having an issue I cannot seem to resolve. I am being refused only on port 80. However port 8080, and 22 (Tomcat and ssh) are available. I am pretty sure this is not an Apache thing, however I ...
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Cannot create new service with xinetd in RHEL6

I've installed the Nagios on My RHEL 6.4(x64) machine. and i added one more module name called "NSCA" for some central monitoring solution.so the setup required add NSCA service detail under xinetd. ...
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1answer
125 views

detect process that executes portscans

I have to administer an ubuntu 12.04 server, where there seem to go portscans to the whole subnet. How can I find out the process that does the scans? pstree init─┬─acpid ...
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361 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: ...
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2answers
3k views

How do I find out what file Apache is serving when a port is hit?

I'm working on a server someone else set up. The server is CentOS 4.6 running Apache/2.0.59 (httpd). They have an update service setup on port 8443. I know it is working but I need to find out what ...
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212 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
67 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 ...
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2answers
78 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?
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0answers
59 views

Can we Bring Up eth1 after removing e1000e modules?

I am trying to setup TCP in RTnet. I am not sure whether its possible. I read that RTnet is not supporting TCP. Is that so? So now I am trying to setup rteth0 as server and eth1 as client. To setup ...
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3answers
388 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 ...
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3answers
2k views

ssh will sporadically hang temporarily on fast connection

I am using Ubuntu 13.04 on my laptop, connected to my router at home. When working from home, I will ssh into the servers on campus, through a vpn, with X11 forwarding. ssh -X ...
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2answers
4k 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 ...
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4answers
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How does the server find out what client port to send to?

As I understand it this is what happens when a client makes a connection request: The server will be bound to a particular port number. The port number is always bound to a listening process. Since ...
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5answers
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How to check whether firewall opened for a port but not listening on the port

We will be deploying a new application to a Server and the application will be listening on port 8443. We have asked Network team to open the firewall for the port 8443 on that server before deploying ...
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1answer
1k views

How to connect to port immedeately, avoiding socket_bind(): unable to bind address?

When running a code that is supposed to read from a TCP/IP port I often get the following message (depending exactly what language have been used): socket_bind(): unable to bind address I know that ...
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2answers
7k views

Killing tcp connection in linux

I have some dead connection in one application which is in hanged state if client machine is dead. ->192.168.1.214:49029 (ESTABLISHED) Is there a way to terminate these option from linux ...
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1answer
522 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 ...
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1answer
111 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, ...
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2answers
148 views

Using Wireshark on Linux to observe coupled HTTP-request and HTTP-respond

I use Wireshark on Linux to observe my HTTP traffic. Other programms like Firefox Live Http Headers show coupled http-request from my browser and http-respond from any server. How using programs like ...
2
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1answer
525 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 ...
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1answer
76 views

Enforce strict outbound ports (or ranges) for protocol

Is it possible to narrow the allowed range of outbound ports that can be used for a specific protocol (e.g. HTTP(S))? I understand that, by default, the system will randomly allocate any available ...
24
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1answer
711 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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3answers
3k 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 ...
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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... ...
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0answers
80 views

Why isn't hydra being disconnected?

I have SSHD running on port 5800 on some machine. (It is a my machine at home.) If I run this manually in a terminal: # ssh someIP -p 5800 The connection is lost because I am disconnected after 3 ...
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2answers
1k 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 ...
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2answers
11k 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.
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2answers
5k views

Ephemeral port : What is it and what does it do?

I suddenly came across the term "ephemeral port" in a Linux article that I was reading, but the author did not mention what it is. What is an ephemeral port in UNIX?
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1answer
111 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 ...
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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 ...
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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 ...
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2answers
698 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 ...
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2answers
123 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 ...
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3answers
430 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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1answer
416 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) ...
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3answers
841 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 ...
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2answers
2k 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 ...
3
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2answers
581 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 ...
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0answers
223 views

No ports can be found using port scan

Problem: I have a laptop and a server (Home-Server) with fc17. They are both using the desktop environment. I am trying to set up a VNC server on Home-Server so that I can set everything up without ...
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1answer
203 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
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1answer
2k 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 ...
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4answers
1k views

TCP dies on a Linux laptop

Once in several days I have the following problem. My laptop (Debian testing) suddenly becomes unable to work with TCP connections to the internet. The following things continue working fine: UDP ...
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2answers
12k views

Fast way to copy a large file on a LAN

I am having some trouble with NFS, and I'd like to try using just plain old TCP. I have no idea where to begin, though. Hardware-wise, I am using an ethernet crossover cable to network two netbooks. ...
2
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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 ...
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1answer
831 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
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1answer
210 views

Socksifying a qemu-kvm using tsocks

I'm trying to socksify a qemu-kvm using tsocks, but I have no success. I don't know if qemu access directly the hardware, skipping the OS or something like that, but I wasn't able to do this feat. ...
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2answers
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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 ...
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3answers
973 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
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1answer
2k views

Run nmap via Tor

Is it possible to runnmap via Tor? When I googled around, I got the impression that Tor uses Polipo / Privoxy, which are socks5 proxies. So any TCP / UDP aware applications should be able to use them ...
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3answers
369 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 ...