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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Can two different services on the same machine use the same port on IPv4 and IPv6?

Say I have two TCP services A and B. A is an IPv4-only service listening on 127.0.0.1:10000. B is an IPv6-only service listening on ::1:10000. Can I start these services on the same machine? That is, ...
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1answer
34 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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1answer
127 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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1answer
10 views

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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0answers
151 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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1answer
29 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 net....
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17 views

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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14answers
10k views

Must TCP use IP?

Is it true that TCP is short for TCP/IP and they mean the same thing? Is it possible for TCP to be built on top of another protocol besides IP?
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1answer
286 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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0answers
89 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 link?...
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0answers
34 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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0answers
18 views

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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438 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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1answer
158 views

TCP server listen and client listen windows software

I am using Windows OS on an amazon cloud AWS with static public IP. On this machine I need to set up a TCP server to listen on port 2204 for raw data that will arrive from a GPS base station over TCP ...
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0answers
62 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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1answer
74 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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2answers
6k views

Do browsers create new TCP connections for each HTTP requests?

So I know that HTTP is basically just a text protocol over TCP, and that TCP is state / connection based. That means that the browser has to connect over TCP to a server before doing an HTTP request. ...
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2answers
377 views

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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1answer
620 views

haproxy- setting up an TCP connection cache for an HTTP server

I am trying to setup a local TCP connection cache to provide access to a remote HTTP server for multiple local applications. I have started to configure haproxy to do this: global log /...
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0answers
35 views

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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0answers
43 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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0answers
124 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: http://www.yxjiaodai.com/ad/?id=1023&url=http%3A//a1819.oadz.com/link/C/1819/3081547/dtMdon4l79FwsIo2JXEHqtdp5eQ_/p007/...
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1answer
106 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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1answer
67 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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0answers
28 views

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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1answer
291 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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3answers
2k views

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 ...
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0answers
38 views

Outgoing traffic using Local(internal) PC IP address to a DDNS hostname

Sorry if the title is confusing. I have two devices connected through the internet. I need device A (Windows Server 2012) to send data down to device B, but unfortunately device B does not have a ...
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1answer
1k views

OpenVPN working with TCP not with UDP

I have successfully set up an OpenVPN server on Debian (raspberry pi model b+). With the protocol set to TCP it works exactly as desired (internet routed through VPN, access to local network machines),...
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1answer
70 views

Serial over TCP

I have a serial device connected to a remote computer and would like to transmit the serial data from this machine over tcp to another computer, both linux machines. Ideally, I would like to link two ...
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0answers
98 views

One side TCP ESTABLISHED connection

On the Server 10.10.3.171 I use netstat to find clients : $ netstat -ant | grep 24225 | grep 10.10.3.169 tcp 0 0 10.10.3.171:24225 10.10.3.169:58591 ESTABLISHED tcp 0 ...
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1answer
673 views

How come LAST_ACK doesn't enter CLOSE_WAIT?

When a TCP connection is closed at one end of the connection - the other end receives a FIN and responds with an ACK. This end of the connection then enters the CLOSE_WAIT state. Once close() is ...
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2answers
8k views

On the Performance of TCP implementations of Linux and Windows

I understand the implementation of TCP stack in windows and Linux are different. Windows uses a congestion control algorithm known as the TCP Reno while Linux uses Cubic. How do the 2 protocols ...
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2answers
5k views

Remotely push DNS server to client via OpenVPN

When I try to push a DNS server via the OpenVPN server-config I don't get that server to be the first DNS server on the connected client system. It ends up being specified as an alternative DNS server....
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25 views

How much upstream traffic should a transfer over TCP produce

When a file is downloaded via some TCP-based protocol, there is also data flowing in the other direction – acknowledgement packages etc. Now if I watch some network monitor, I wonder if all of the ...
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0answers
57 views

Does Fast Retransmit and Retransmission Timer work at the same time?

When Fast Retransmit is implemented, if I received packet 1, then I will send an ACK that says I need packet 2, and then if I received packet 3, I will send a duplicate ACK that says that I need ...
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0answers
38 views

TCP Retransmission on the receiver side

How does Wireshark knows that a packet on the receiver side is being retransmitted. I mean it makes sense on the sender side: Wireshark sees two identical packets (with the same sequence number) being ...
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0answers
109 views

How to change the current TCP timestamp value for Linux?

Linux normally sends a TSval field that corresponds to the current uptime. I would like to overwrite this with a user-specified value. # 4 hours after boot: > outgoing TCP packets have TSval ...
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1answer
2k views

Why is the FIN flag in TCP called FIN?

There are some flags in TCP. I already understand what other flag names come from, such as SYN stands for synchronization. I also know that FIN is used to close a connection. What I don't understand ...
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1answer
68 views

How much time does TCP waits before retransmission?

If I have a window size of 8 KB, then when 8 KB are sent to the other side and no ACK has been received, TCP will not send anything more until an ACK is received. But what if an ACK is not going to ...
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5answers
27k views

Access Methods to a computer Using MAC Address

I have my own wifi network at home & recently when I checked the active clients on the wifi I found out the there is one active client. Router shows the MAC address of this client and I want to ...
0
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1answer
77 views

Not able to login to Tuleap after full installation due to TCP IP port configuration

Not able to login to Tuleap after full installation, as all the ports are in listen mode and 9091 port is not visible in ports.How to over come this and solve. With IP address we are getting tuleap ...
0
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1answer
103 views

Linux TCP buffer simulation

I would like to run simulations on the Linux TCP receive buffer to find out how big my buffer has to be. Is there any software available to perform such simulation? It would be handy to be able to ...
3
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1answer
135 views

Why does firefox send TCP packets even when idle?

I run firefox on Debian. I made a clean install with no cookies, or no information input from my side. I've also disabled all mumboo-jumboo healthy and crash report tracking. I've disabled 'shared ...
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3answers
764 views

How to manually send an ARP request

I recently sniffed with Tcpdump a packet "ARP, Request who-has 192.168.2.3 tell 192.168.2.2, length 28". I would like to reproduce this message, and to send an ARP request from my laptop to any IP I ...
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0answers
205 views

Tcp connection target machine actively refused

I have a simple TCP client/server program on two laptops. The server should work fine as I use "netstat -anb" and the server shows up as listening, "0.0.0.0:102", then my client connection failed, ...
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3answers
71 views
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1answer
377 views

Which congestion control algorithm is used by the TCP stack in OS X?

What congestion control algorithm is implemented in TCP in OSX 10.9? I would like to know if it uses NewReno, or something newer like Cubic in Linux.
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1answer
192 views

TCP socket to serial port

Is is possibile to remotely access a serial port by tcp socket server? Exists this kind of software? It is the opposit of this question: Any free application to redirect serial communication to TCP/IP?...
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15answers
75k views

How do I kill a process that is dead but listening?

I'm developing an app that listens on port 3000. Apparently there's an instance of it still listening to the port because whenever I start it, it can't create a listener (C#, TcpListener, but that's ...