TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.

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Samba not connectable “Go away, we're not home”

I'm having an issue connecting to my dedicated server using samba. The server is a debian (squeeze) box running a samba server, only small modifications have been made to the default config and the ...
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777 views

tcp port numbers reused on wireshark

I used raw socket to build a tcp client program on machine A to reproduce tcp 3-way handshake with a simple regular tcp server on machine B I captured packets on the client host and server host, and ...
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400 views

MySQL crashes when connecting from localhost with tcp (UNIX sockets work)

I have Ubuntu 12.04 running MySQL server 5.5.24. I can connect with mysql --user root -p. status shows me : ... Connection: Localhost via UNIX socket ... When I try to connect with mysql --host ...
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56 views

Most network protocols occasionally fail

My Windows 7/64 machine has suddenly started to act funny. Everything will be running fine, when suddenly most network access methods will fail. These things continue to work: Accessing network ...
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187 views

Is there a software that allows RS232 sniffing and TCP/UDP listening

I am looking for a software that would fulfill the following requirements: Able to "sniff" communication over RS232 (like PortMon and Advanced Serial Data Logger) Able to listen to a given ...
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37 views

Is it possible to edit TCP and UDP packets?

Is it possible to edit the UDP and TCP packets a program sends? For example, we have a program that sends some information to its server. But we don't want to send some information that might be ...
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87 views

Iperf tests in reverse direction

I used iperf to measure the max throughput for TCP connection between two ubuntu machines. Both the machines were directly connected be means of a 1Gbps cable. When I performed iperf tests i obtained ...
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55 views

why the ping doesn't get a reply?

I have an embedded board that has the CFE, a minimal loader. I have a host machine - linux FC16, where I am running a dhcpd server. My interface is p3p1. Here are the details of the ifcfg-p3p1. ...
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58 views

Linux Kernel TCP socket functions

So I have been looking through the Linux Kernel v3.8.0-19-generic source code and I noticed that the proto struct, whose members are virtual functions for socket operations depending on the particular ...
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60 views

Delete Hung TCP Sessions with SNMP

What I am trying to do, and failing horribly, is to close a TCP connection... I am trying to do this via SNMP and the functionality that is provided in the TCP MIB. First, I look at all the ...
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92 views

Windows 7 / PuTTY drop IPv6 TCP connections on brief outages

This is an IPv6-version of the following question: Why Windows 7 / PuTTY drop TCP connections even on very brief outages? After moving from IPv4 to IPv6, I've noticed that my IPv6 connections would ...
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81 views

No response received from github ssh randomly

My git pull started to stop working randomly with this error $ git pull ssh: connect to host github.com port 22: Connection timed out fatal: The remote end hung up unexpectedly I tried debugging ...
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119 views

TCP/IP resets (Linux, SSH, RDP, ADSL router)

I have an ADSL router (model Pirelli DR A226G) that seems to cause dropped tcp/ip connections (not ADSL connection per se). I have tracked it using Wireshark and captured a few cases and they always ...
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135 views

Load TCP New Reno protocol

I am doing some test of the congestion control protocols and I cannot find how to load the protocol New Reno. I loaded a lot of protocols like Reno, Vegas, Hybla, Bic, Cubic, etc using the sysctl ...
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275 views

How to use NetLimiter to block inbound TCP traffic?

I'm using NetLimiter to block TCP traffic. (Rule type: Firewall, Direction: In, Action: Deny) I can block outbound, but not inbound. You can try blocking inbound TCP on Chrome to see it is not ...
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173 views

Artificial network delay tcp/udp (bigger ping) for defined application? (windows)

I have a game where people can easy detect who i am looking at my ping, i want to make my ping highter. How can i set network delay for all network connections for defined application?
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170 views

Tunnelling TCP connection through NAT

My server is in my school's NAT and my desktop computer is in my home NAT. I want to SSH to my server from home. I normally used school's VPN, but recently for some reason I can't. So I'm looking for ...
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102 views

TCP connection not timing out, visible on server but not client

On the server both the application and netstat show a connection open. The client however lists no such connection, and the client software is definitely stopped. I'd already lowered the TCP ...
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100 views

How to route none http request in pound.cfg

I'm trying to route all request that point on the port 3050 to another host, here is what i usually write in the /etc/pound/pound.cfg: ListenHTTP Address 10.165.30.58 Port 3050 ...
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319 views

Can not open port 6000 windows xp

I am trying to connect to macincloud using their software and can not. They told me the reason is port 6000 is not open. I spent 3 hours on the phone today with ATT making sure the 6000 port was open ...
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685 views

Iptables port redirecting. Rule doesn't work or show up in iptabels

I'm trying to redirect some incoming TCP traffic on port 443 to port 999 with iptables in an Ubuntu VM. I am using sudo iptables -t nat -A PREROUTING -p tcp --destination-port 443 -j REDIRECT ...
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319 views

Create a VNC proxy with authentication

We have a bunch of VNC servers located on our local network. We wish to give external customers access to these VNC servers, via some sort of "middle-man" software solution which can handle ...
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337 views

iodine fails its ping test

I'm trying to get iodine working on my Ubuntu machine. The server is working fine, but when it try to establish a connection, and change the route table using the default iodine-client-start script i ...
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364 views

HP G61 Notebook: TCP seems to be dead

Can't say I'm much of a Windows expert, but this is somewhat of a weird occurence. I'm in front of a HP G61 Notebook laptop with Win7 that has connectivity problems. I mean that it's connected to the ...
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38 views

Linux message: Possible SYN flooding on port 25. Sending cookies

I have a Linux CentOS server online. At my console this message appeared: possible possible SYN flooding on port 25. Sending cookies. See SYN flood and SYN cookies. I have done an Apache JMeter ...
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11 views

How do i control a epson projector using putty

Currently i have been messing with a Epson emp 7900, trying to get it to be controlled by a python script. I have currently got a problem where if i send "PWR OFF" it will return "ESC/VP.net@" ...
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29 views

Multipath tcp application-level performance measurement

I am working on a project related to Multipath tcp and I want to measure the goodput and the RTT at the application level. I don't want to use a traditional tool(netperf, iperf, ...) and I want to ...
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25 views

No response to ping of specific size

ping <anything> -s 473 does not receive a single reply. ping <anything> -s 476 works, as well as ping <anything> -s 472 but no size inbetween. What could be the reasons for ...
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30 views

iptables error “FIX ME! implement getprotobyname() bionic/libc/bionic/stubs.c”

When I do this rule, the error shows up iptables -A INPUT -p tcp -m tcp -m multiport ! --dports 80,443 -j DROP I've also found some solutions. getprotobyname() just converts protocol names like tcp ...
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16 views

Inconsistent connection to Websocket on embedded device

I am trying to set up a basic Websocket echo server on an embedded device. I'm testing the server through a very basic webpage, which simply connects upon load and sends a short message ("test") and ...
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14 views

Tons of connections to TCP 135 on another host on the LAN

I am facing a scenario where one server has tons of established connections to port 135 on the DB server on the same subnet. So when I do netstat -nap tcp, I got pages of pages followings, random ...
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55 views

Ethernet port on Linux machine not recognizing ethernet connection with embedded device

I have an atmel at91sam7x256 microcontroller that I would like to use for a TCP/IP communication. The very first step of my project is to be able to "ping" my board given its IP address. I have its IP ...
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38 views

Hiding port number from address.

I have centos 6.5 running some web apps. Currently due the following port forwarding rules, I am only able to access my public content using 127.0.0.1:8080/ Is there anyone to just use 127.0.0.1 ...
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37 views

How to use netperf on specific NIC port?

I have two servers, SERVER and CLIENT and each server has its own onboard 1 GbE ports, and its own NIC with a 10 GbE port. SERVER and CLIENT are interconnected on both a 1 GbE switch (administrative ...
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478 views

How to send message to virtual serial port created with socat?

I am using socat to create a virtual serial port on linux socat -d -d PTY,raw,echo=0,link=/dev/ttyVA00 PTY,raw,echo=0,link=/dev/ttyVB00 which prints socat[31640] N PTY is /dev/pts/2 socat[31640] N ...
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27 views

Setting/clearing packet's TCP flags with iptables

I know iptables can match packets with certain TCP flags using --tcp-flags. But how do I set or clear some flags on a matched IPv4 packet?
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29 views

UDP causing problems with other connections

I have implemented a file transfer program on Windows 64-bit platform using winsock API. I am using a 1Gbps connection. When I transfer files using TCP protocol, I am getting only 320 Mbps. when I ...
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59 views

How do I drop a TCP packet matching a certain signature on windows (e.g. firewall-based)?

I am searching for a way to stop a TCP packet with a certain signature and connection from reaching an application. The packet may be dropped completely. The packet contains the byte signature [42, ...
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27 views

What impacts does RTT have on the behaviour of TCP?

How does round-trip time impact a TCP connection's behaviour? I know that the throughput of a connection with a high RTT is lower than the throughput of a connection with a low RTT but how does RTT ...
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21 views

TCP windows scaling in Windows 7 works only alternate times

I am running iperf TCP client in loop from another program. I am getting high and low throughput alternate times. I also tried to use fresh installed Win 7. This behaviour is not seen in Win XP and ...
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16 views

How to keep socket visible after closing the connection?

Is it possible to configure Linux to keep a tcp connection visible for netstat/lsof after being closed? (doesn't matter the connection state). I need to detect it with netstat/lsof but if the ...
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224 views

how to kill a tcp connection in solaris operating system?

A client program connects to my server program written in JAVA via TCP connection (ServerSocket). I want to close the TCP connection between these two programs with a Solaris command or tool for ...
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16 views

TCP behavior in microsoft products

What happens when a TCP SYN segment is received on a closed port? Does windows send a RST or it just ignores it?
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158 views

What exactly TCPIP parameter StrictTimeWaitSeqCheck does?

From http://technet.microsoft.com/en-us/library/cc722796.aspx: This value indicates that a socket should not be reused before the time specified by TcpTimedWaitDelay passes. So, if it is 0, ...
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25 views

Switching ethernet interfaces in Fedora

I am working on a computer which has two gigabit ethernet interfaces. This is the current configuration: PORT 1 (INTERNET) PORT 2 (SPP) Port 1 connects my computer to the internet whereas ...
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85 views

What changes to my network settings in Windows 7 can I make to achieve lower latency for gaming?

What changes to my network settings in Windows 7 can I make to achieve lower latency for gaming? I have heard of changing TCP settings in the registry, but I have also heard conflicting information on ...
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458 views

connect to a serial device via TCP socket

My setup is this: serial device ttyUSB0 connected to laptop A software that opens TCP socket to listen and write to, also runs on laptop A (linux) My goal is to pipe data from/to serial device ...
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58 views

Does Windows 7 still require the tunage of the TCP Buffer sizes?

I'm getting very slow single-stream downloads on a 1Gbps connection when using some ssh-based app (about 1MB/s or so) over a 100ms latency link. Is this related to some bug in the app, or would ...
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37 views

I think that someone else is entering my computer for long, sth like back orifice. I then got TCPView. Now, what do I do?

I got some variations of the name of my own computer going on in TCPView, for instance. I wonder whether that means another computer, like in one instance the name appears in capital letters, in ...
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232 views

Can't telnet: TCP connection doesn't get established

I am having issues with telnet from a machine. TCP connection is not getting established. SYN gets sent out and SYN_ACK comes back but not sure why the ACK is not getting sent back. I am guessing ...