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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Is there a way to completely disable TCP keepalive?

I'm trying to disable TCP Keepalive in a linux machine. If I set the three keepalive parameters to 0, the machine refuses connections. sysctl net.ipv4.tcp_keepalive_time=0 sysctl ...
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Ubuntu IPTables

I started hosting my game-server on Ubuntu Linux 14.04 I am having an issues ، some enemies/bug abusers log in 2+ characters in the same second then they spam a certain spell/word that lags/stops my ...
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How to know that I passed the firewall from the TCP connections?

In my company, in order to access some intranet-sites, I have first to login to webpage (which I suppose is a firewall or something) with my account. If I login from FF for example, I can access the ...
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NAT doesn't allow TCP ACK for sent TCP SYN

We are using TCP Simultaneous Open for connecting TCP socket. Lets call one SideA and other SideB. From the wireshark log I see that first two SYN sent from SideB is blocked by SideA NAT. Then SideA ...
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2answers
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How does a Router/Modem obtain the Port Number from an IP Datagram?

The IP datagram header is a layer below the TCP segment which contains information on the port. Therefore before a firewall can inspect a port number, must the IP datagrams be rebuilt into the TCP ...
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Wireshark FTP multiple ACK?

I'm trying to visualise somes frames that correspond to a file transfer between two machines on Wireshark. The thing is that there are multiple ACK for each FTP-DATA segment and I don't understand ...
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49 views

Replay captured TCP packets

I captured a tcp traffic using wireshark and saved the traffic in pcap file. I did two tests: Test 1: sudo tcprewrite --infile=capturedtraffic.pcap --outfile=temp.pcap ...
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40 views

Connection remains flagged as ESTABLISHED even if host is unconnected

I am working on a Linux embedded distribution and I need to monitor incoming and outcoming connections (if they are still actives etc.) and I am experiencing issues because I noticed that, even if the ...
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29 views

Windows 7 pc opening port 139 from random IP addresses

When I run CurrPorts (a TCP monitoring tool for nirsoft) I get the expected output plus entries that I do not understand. My LAN is 192.168.1.x. My pc is set to a static IP of 192.168.1.12. But I find ...
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36 views

Ways in Which TCP/IP Stack Fails?

In a variety of books and learning materials, we're told that if pinging the localhost/loopback address fails, this is a sign of a malfunctioning TCP/IP stack. What we aren't told is why/how this may ...
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43 views

TCP slowstart by threshold value

I was doing excercises out my book. But there are no answers in the book. This Question is very interesting to me. Does somebody now the answer and why it that answer? A lonely sailor on the Pacific ...
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48 views

Unstable Transmission Rate in TCP by Packet Loss

Is it true that TCP does not provide a stable transmission rate, because TCP always keep increasing the bandwidth until there is a packet loss?
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TCP on the same (server side) source port to multiple (different destinations)?

Question 2 Is it true that a TCP server may send segments with the same (server side) source port to multiple (different destinations)?
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Windows 10 dropping TCP connections after 30 seconds

On my Laptop (DELL Latitude E5530) with a completely fresh Windows 10 Enterprise installation any TCP connection gets disconnected after close to exactly 30 seconds. I noticed it first when Skype for ...
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3answers
70 views

Relation between TCP conversations and TCP streams in Wireshark

I have read about Conversations and TCP Streams but I'm still a bit unsure how they relate to each other if they are on the same layer. For different layers, it's clear to me that e.g. an IP ...
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1answer
21 views

Connection timed out when connecting to a remote tcp port

I have deployed my application on Linux CentOS. The app connects to a remote TCP port but it throws a connect timed out exception. I tried to connect it via telnet but the port doesn't respond. I am ...
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205 views

How to increase RWIN Value in Windows 10?

We all know that a lot of things have been deprecated and there was also the introduction of auto scaling in earlier windows versions. Right now after using this analyzer ...
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1answer
35 views

TCP connection only working one way on my local network (trying to connect with Synergy)

I am using Synergy to connect my desktop (GNU/Linux. connected via cable to router) to my laptop (OSX ElCapitan. connected via WiFi). It works like a charm if I use the laptop as the server; From ...
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1answer
43 views

How to list socket options of running processes?

Is there a convenient way (e.g. a readily-available command or a program that I can write using standard system calls) to list socket options (e.g. TCP_NODELAY) of an open TCP socket of some running ...
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29 views

Kill TCP connection in VMware ESXi 5

If there anyway to kill a tcp "TIME_WAIT" state connection in VMWare ESXi~ # esxcli network ip connection list Proto Recv Q Send Q Local Address Foreign Address State World ID ...
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1answer
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Configure Wireshark to capture any packages between host machine, and guest (VM)

I'm new to this whole Wireshark thing. I have a VM running inside my local Mac via VMWare Fusion. VM IP Address : 172.16.139.129 Mac IP Address : 10.0.0.4 I want to capture http connection between ...
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2answers
37 views

How can one block a port without administrator privileges?

I have found that binding to a port with a Java program prevents other applications from using the port in question. However, if an application is already using the port, a Java program cannot be used ...
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2answers
44 views

Raw TCP on Chrome OS

I have an Acer Chromebook 13, with an ARM processor, and am trying to connect to my friend's server via TCP. I have tried all of the promising web apps for Chrome but they either will not connect or ...
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137 views

DBus over Network (TCP)

I'm trying to communicate with a remote DBus (i.e. IP 10.100.20.101) from a host (i.e. IP 10.100.20.102) - X86_64 platform to ARM development board. I've tried the solutions from here but it caused ...
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Windows 7 frequent download interruption

I just upgraded to Windows 7 Pro from Home Premium, and now almost all downloads (Youtube videos, online games, ftp/http downloads) are interrupted after a random length of time. Sometimes the ...
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52 views

Why are TCP Packets going from my pc to server owned by EdgeCast Networks, Inc.?

I am seeing a lot of entries like this in my Netgear DGN 1000 log for the last few weeks: Wed, 2015-11-04 20:36:56 - TCP Packet - Source:192.168.0.2,63272 Destination:68.232.44.114,80 - [BLOCK] ...
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TCP Dump received from Verizon, along with an abuse notice

Apologies in advance if this Question is not a good fit for your forum, but I hope it is and someone can help. I'm a FIOS customer and received from "abuse@verizon.net" a TCP dump as part of an email ...
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59 views

Killing TCP connection on Windows via cmd prompt

There are already at least two similar threads on SU both having either outdated answers or answers that suggest using GUI. Thus the following programs are NOT what I'm looking for: wkillcx - that ...
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1answer
32 views

ACK seq number and number of retransmission

In the above TCP stream, I notice that the expected next seq number of no.9 TCP packet is 1902. But the following ack number of the ACK packet is 1903, which is 1 more than 1902. I'm wondering ...
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57 views

How to check the TCP Variant in Ubuntu

I am using Ubuntu 14.04 LTS with Linux Kernel version 3.13.0-34. How to find out what is the default or what is the TCP variant being used.
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How do the HortonWorks and MAPR VMs receive connections on localhost?

I just downloaded both the Hortonworks and the MAPR VMs for VirtualBox. Both of them start up VirtualBox and then give a UI that looks like this: What I don't understand is this: how do the VMs, ...
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90 views

TCP connect fails with certain websites

I am running Windows 10. I am unable to browse a few seemingly random websites (CBS.com is one of them) using any of my browsers, although I can successfully ping all of them. Also, other computers ...
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24 views

TCP settings not sticking after reboot (Yosemite)

I'm changing the following settings in the Terminal, and after I reboot, they return to their default values. sysctl net.inet.tcp.always_keepalive=1 sysctl net.inet.tcp.keepidle=20000 sysctl ...
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Request Tracker on linux gives CLOSE_WAIT

Hi I have an RT installation on CentOs 6.7 and RT 4.0, I can log in and all, but after a while I am seeing CLOSE_WAIT socket is created for each selection that I make on the dashboard. Eventually the ...
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156 views

Which of the following protocols can use multiple TCP connections between the same client and the server?

In one of the pairs of protocols given below , both the protocols can use multiple TCP connections between the same client and the server. Which one is that? HTTP, FTP HTTP, TELNET ...
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40 views

How to determine TCP socket idle duration on Linux

How can I see how long a TCP connection has been idle for? This question shows how long the connection has been "up" for. What I'm looking for is: how long there has been zero traffic on the TCP ...
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28 views

unknown local address in TCPView

I'm looking at connections in TCPView, and I'm seeing "red5" in the "local address" column. This doesn't appear to match any computers on my local network, the names of which I have seen from time to ...
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TCP Rentransmission when connecting sepcific website

Question: I'm an administrator of couple of websites. Every website is set on the same server provided by linuxpl.com. The server ip is: 95.211.176.132. The problem is, when I try to reach the server ...
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208 views

TCP ESTABLISHED connections timeout applicable for inactive connections?

The default timeout for TCP connections in ESTABLISHED state seems to be 5 days. I was hoping to decrease this to like an hour instead (net.netfilter.nf_conntrack_tcp_timeout_establishe=3600) as some ...
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40 views

iptables SNAT target and TCP ACK packets

I need to establish a TCP connection where the client is spoofing its IP for all outgoing traffic. My first attempt was to add a rule to the POSTROUTING chain like so: iptables -t nat -A POSTROUTING ...
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45 views

how to connect between two virtual machines in different computers via TCP

I am trying to connect two different virtual machines together, with each on a different computer. I tried using NAT and port forwarding that is, when the client tries to connect on another computer ...
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What TCP / network tuning should be performed in Windows 7 for best internet performance without reasonable risk of causing issues?

I'm wondering what network / tcp tuning should be done in Windows 7 to ensure best performance (yet without reasonable risk of causing issues). Here's what I have so far (the below commands get run ...
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What causes these corrupted downloads and spurious retransmissions?

I encountered many corrupted downloads recently. Sometimes compressed files wouldn’t open or checksums would not match. Sometimes images on Websites would just be grey (or a wild mix of colour) after ...
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What is this no buffer for socat connect error?

I have started to receive this error while using socat: socat[1441] E connect(3834, AF=2 <ip>:<port>, 16): No buffer space available And have found no clue what so ever as to what may ...
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41 views

Change TCP/IP settings automatically depending on connected network

I use Simple IP Config which lets you create profiles and you can manually change them when you need to. I'd like that to go one step further and automatically change the adapter's TCP/IP settings ...
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54 views

How to block HTTP 302 redirection package by matching a specific string on Location?

The HTTP response I want to block has: Header HTTP/1.1 302 Found Location: ...
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55 views

Why a POST request uses the PSH flag in the first packet?

I'm trying to understand the behaviour of the POST HTTP Transaction. When there is a GET request with a long URI that needs more than one packet to be sent, the PSH flag is used in the last packet to ...
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How long does NAT keep a TCP translation field in it's table

I was wondering if I could create a TCP client on machine A and connect it to a remote host (S) and then close the connection from client side and create a TCP listener on the on the same machine ...
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101 views

Differences between TCP receiver and transmission window

After reading this question I'm still confused about the relationship between the receiver window and the congestion window in the context of TCP based communications. The answer states that the ...
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Does the sequence number of TCP packet headers wrap around?

I was wondering, since the sequence number in a TCP header field is randomly chosen during the handshake and is gradually incremented as packets are exchanged, what happens after 2^32 - initial_seq_no ...