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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How are ports and URI schemes handled by a tcp/ip server?

I am working with the lwip tcp/ip stack on an embedded device, and I'm trying to understand how it all works. I've been looking through the documentation and code, but I'm confused by how ports and ...
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TCP vs UDP. Sending data on a closed port

I try to understand differences between TCP and UDP packet on the error-checking. I know that UDP packets are connectionless and doesn't care that the packet will arrive the destination safely. And ...
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16 views

How can I turn on ECN for Mac OSX?

I'd like to run some networking tests with Mac OSX 10.8 and using the ECN option. However I cannot find any documentation on how to configure it. Does anybody know how to alter Mac OSX TCP networking ...
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62 views

For what does ssh use UDP?

Wile doing research I noticed that SSH both uses TCP and UDP. I completely understand the use of TCP, but UDP seems a bit strange. Why would I use an "unreliable" transport protocol with minimal ...
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36 views

Why HTTP response is split in 2 parts: header and body?

I'm trying to understand why a single HTTP response is split in 2 parts in the following setup: Requested resource is protected by HTTP Digest Authentication on server side. Communication is ...
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40 views

Port Blocked by Network Adminstrator how to bypass it? [closed]

I use a gaming client called "steam". My network adminstrator (college sysadmin) has blocked the steam port.Also, steam does no allow remapping ports. I tried various VPN services like Hotspot Shield, ...
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25 views

How to add code into the linux kernel?

I am studying how to analyse and evaluate the TCP/IP protocol stack of Linux. My goal is to study the performance of the tcp/ip protocol stack as a whole, to study the time cost of each layer and ...
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26 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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14 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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51 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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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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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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24 views

Restrict SSH server tunneling port

I have a SSH server running OpenSSH. I want to use it to setup a SOCKS server so that my friends in China can use it to access websites such as twitter. I want to enforce two restrictions: 1. no shell ...
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23 views

Simulate tcp window full on ubuntu

I have 2 ubuntu boxes. In between them is a firewall. I am trying to simulate tcp window full condition or in other words, I want the ubuntu server to send a tcp window full flag to client. Here are ...
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Windows Server 2012 cannot access web sites

I have a Windows Server 2012 that has gone a little crazy in the last 24 hours. It can't access any websites, internal to the network or on the web. I can ping google.ca for example and it resolves ...
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How to force a process transmit over UDP instead of TCP?

I 'm running an ffserver process on a Linux machine, in order to achieve video streaming via ffmpeg. However, there is a delay on video streaming. On ffserver configuration file I define Port 8090. ...
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37 views

DNS Resolver for Windows over TCP

I know that DNS uses UDP with Port 53 for DNS queries. However, at my place sometimes UDP requests are blocked and DNS fails. I know that there is protocol for DNS over TCP and many public DNS servers ...
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20 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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61 views

Session layer in OSI vs TCP/IP

I'm sort of confused here: According to several illustrations I've seen and material from Cisco the session layer from OSI is part of the application layer in TCP/IP. This makes no sense to me since ...
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TCP/IP minimal size

I am using a high level language on a PC to send a message via TCP/IP to a remote device which is an embedded device. I am sending relatively small messages (< 255 bytes). I must assume that there ...
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176 views

Why does writing IP addresses this alternate way work, and is there a practical use case for it? [duplicate]

Recently I saw an incorrectly typed telnet command, and I saw that "regular" numbers were interpreted to IP addresses. I tried this myself in Windows and the same behavior is shown there, so obviously ...
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62 views

Free official documentation for cables and models? [closed]

I've been looking through the ISO and IEEE sites for official documentation on the Open Systems Interconnection (OSI) model, TCP, and a range of cable standards (5/5e/6). However, other than on the ...
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Is DNS query a UDP or TCP?

I know that when we first type an address on the URL and enter. The DNS query starts. I don't who initiates, but my guess is application will only initiate the DNS query. The DNS query already knows ...
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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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18 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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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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51 views

How to calculate TCP network speed

So basically this is an easy question, but not an easy answer. How do i calculate the download and upload speed in order to make program this in c#? I'm not sure how to take latency into account. I ...
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462 views

Communication possible between 192.168.0.x and 192.168.1.x?

I have a problem I encounter on a regular basis. I have an access point with a fixed 192.168.0.x IP address. My network is 192.168.1.x. The problem is when I plug the access point into my network, it ...
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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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56 views

Throughput decreases after MTU 5000

I am trying to test throughput between two computers directly connected through 1 GbE and testing with iperf. I am getting a throughput around 980Mbps when MTU is between 5000 and 5050, however it ...
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62 views

Why TCP performance degrade with bidirectional traffic?

I've made a simple experiment on TCP transportation performance. The experiment is as follows: There are two machines, A and B, each installed with Ubuntu 12.04 Server. I've installed "iperf" on ...
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75 views

Is it possible to create a WiFi TCP socket between two computers in a LAN?

Here is our setup. The FEZ Cobra II (WiFi) Single Board Computer with a RS9110-N-11-22-04 WiFi module and running the .NETMF 4.2 The documentation says that: This allows for real "Socket" ...
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60 views

Can using UDP and OpenVPN lead to file corruption?

I know with TCP that it always checks your files to ensure nothing got fragmented or lost or destroyed. So if I use UDP for OpenVPN to download files or access an internal network, does that mean I ...
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Capture packets from other machines in local network

Is it possible to capture packets from other local machines on my Mac? They are primarily all wireless as well, if that makes it any easier.
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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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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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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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309 views

What's up with port 8080 on my OSX box?

I thought a web server process I brought up was listening on localhost:8080, and tried to connect to it, but kept getting connection reset errors. As it turns out, I was mistaken and my process was ...
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126 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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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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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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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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Does TCP verify data all at once or as a packet by packet verification?

I know that TCP uses verification to ensure accuracy of data by sending to the server. My question is does it verify everything at once or as it comes in? Quick Example: Let's say I am loading the ...
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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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SYN-ACK not received

On a standard TCP connection between server and client, I have this issue: the SYN-ACK is not received from the client, while it is sent from the server. I could see this on Wireshark from both server ...
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314 views

Network issues, resolving host

My network connection randomly drops for a 5 minutes or so when I'm online. It always happens when I boot up my computer. I can tell because it says:resolving host in Chrome and I can't ping any ...
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42 views

How to configure the physical machine and virtual machine?

If I want to transfer data between the physical machine (windows operating system) and virtual machine (Linux real time operating system). Could anyone please explain about configuring the data ...
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How does an ADSL modem tell which local client to associate with each response from a server?

Does an ADSL modem generate a random string for each request I make and when response comes it directs it to my computer (but not to my phone)?
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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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Is the same port acting as both client and server?

i find something strange in this netstat output. the output is taken using netstat -a -n -o -p TCP command on win 7. Proto Local Address Foreign Address State PID TCP ...