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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39
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2answers
16k views

How does Router know where to forward packet

If several computers with local addresses (192.168.0.#) are connected to a router and each computer opens a web browser and requests a page over HTTP, when these TCP:80 packets are sent out, the ...
37
votes
4answers
75k views

What does “On-link” mean on the result of “route print” command?

I'm using Windows 7. When I type "route print" under command prompt, I get a IPv4 Route Table with several "On-link" values under the Gateway column. For example, like this one: IPv4 Route Table =====...
12
votes
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. ...
9
votes
5answers
901 views

What ports are used by an application [duplicate]

I'm testing an application which opens its own ports (acts as a server for these ports, hence listens at that ports) and where the same application connects to ports bound by other applications (acts ...
4
votes
2answers
6k views

Detect what outgoing ports are bypassed by firewall

My school has a firewall which limits most outgoing ports. There're only TCP/80, TCP/443, TCP/21 allowed. Is there's a way to find out all the outgoing port allowed by the firewall? My current idea: ...
2
votes
1answer
2k views

Is it possible for a PC to use two net connections simultaneously?

We have two net connections in our office - a 10mb Wired DSL provider and a 3mb Wireless backup provider. The wireless is a backup, but it has the advantage of 3mb upload speeds whereas the wired is ...
13
votes
5answers
18k views

How do IP answer packets reach their destination inside of a private LAN?

This is a little theory question that has been confusing me for a pretty long time. Basically, if we are inside of a private LAN, and we want incoming packets to reach, for example, an HTTP server ...
20
votes
5answers
15k views

Ethernet vs TCP vs IP?

What is the difference between Ethernet, TCP, and IP in simple (simple abstract) terms? Please do not copy from Wikipedia...
11
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2answers
13k views

How does circumventing IP restrictions through DNS work in the case of hulu.com?

I just heard from an australian guy that it is possible to watch hulu.com from Australia (which is actually restricted by country IP checks) by using certain DNS servers. Now I was wondering, how ...
6
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4answers
21k views

what is TCP Half Open Connection and TCP half closed connection

I am trying to understand what is the difference between TCP Half Open Connection and TCP Half closed connection can any one tell what exactly are they?
3
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1answer
8k views

The best way to do TCP/IP over USB on Linux

I want to establish a TCP/IP link between two Linux machines that have several USB 2.0 ports as the only connection options. Since both host and slave ports are available, I can connect them via a ...
10
votes
1answer
7k views

Why Windows 7 / PuTTY drop TCP connections even on very brief outages?

I have a small local network that piggybacks on a captive WiFi, and I use ssh on OS X with -oServerAliveInterval=240 and PuTTY 0.62 on Windows 7 Professional for establishing connections to my Linode, ...
6
votes
3answers
16k views

How exactly does a proxy work?

If I want to connect to say, IP 100.100.100.100, Port 80, my computer will send a tcp packet with this adress into the wire. Now If I use a proxy server say, 200.200.200.200 Port 8080 (such kind of ...
10
votes
3answers
2k views

What do the numbers used in a IPV6 address mean?

I am trying to understand IPV6. I have a server with the following IPV6 address: 2607:f750:0:3f::f59. I don't understand what the numbers mean. It looks totally different from an IPV4 address. ...
4
votes
1answer
3k views

What is the purpose of ports?

I have a few questions in regard to the following explanation of ports I found. The Application layer talks to the Transport layer through a port. Ports are numbered and standard ...
4
votes
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....
3
votes
1answer
190 views

What happens when I terminate a process and the socket send buffer is not empty?

In Windows (and probably in other operating systems), if a process has a TCP connection with another process on another machine, and then I terminate the process, an RST packet will be sent to the ...
1
vote
2answers
10k views

Minimum size of the data part of TCP segment

My question has two parts: I know that the "data" part of an Ethernet frame can be 46~1500 bytes. Considering the IP header of 20 bytes + TCP header of 20 bytes, the minimum "data" size of a TCP ...
1
vote
2answers
1k views

TCP/UDP hole punching from and to the same NAT network

I was wondering if tcp/udp hole punching would still work when you are in the same network (behind a NAT), and what the packet's path would be. What happens when using hole punching on the same ...
0
votes
1answer
540 views

How do I establish a connection between 2 computers on different subnetworks?

computer A(192.168.1.134) needs to establish a UDP connection to computer C(192.168.0.30). As you can see both are on a different subnetwork. Now I have computer B which has 2 IP addresses, one for ...
0
votes
2answers
969 views

Understanding port forwarding and NAT

I've got some confusion about port forwarding vs NAT. I know the problems NAT causes for P2P, and that there exist some solutions to it (STUN,TURN,etc) which require a relay server to setup direct ...
9
votes
6answers
8k views

Port scan revealed port 1111 open. What is it?

I am new to systems administration and have a new server running a website with http (at port 80), https (at port 443) and ssh (at port 22). I did an nmap port scan using my personal laptop and other ...
4
votes
9answers
3k views

How to make Firefox use TCP for DNS

I want to use TCP for DNS, to bypass my ISP's slow and broken DNS servers. I'm not using (and don't want to use) a proxy. Note: I want to use DNS over TCP because if I use it over udp, no matter what ...
3
votes
2answers
2k views

How to prove provider is blocking incoming traffic on some ports?

I hope this is not too much focused on home networks, because that's where I hit the problem, but I think it may be of general interest nonetheless. I have a cable connection (Cisco EPC3208) and a ...
2
votes
3answers
1k views

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 ...
1
vote
1answer
85 views

is it possible to update tcp window scaling factor after 3-way handshake by sending a syn/ack?

tcp window scaling factor is notified during 3-way handshake period is it possible to update tcp window scaling factor after 3-way handshake for example, by sending a SYN/ACK with tcp header option ...
1
vote
1answer
481 views

How can I detect long-lived connections and mark them for shaping

I would like to detect TCP connections which have been open for more than one minute (or for greater than N bytes, or M packets), so I can classify them as bulk traffic ("downloads") and de-prioritise ...
1
vote
1answer
6k views

How to set TCP/IP abort interval or timeout in Windows XP?

Does anyone know how to set the TCP/IP abort interval or timeout in Windows XP? In my machine, when I open http://129.129.129.129 in IE, Firefox, or Google Chrome, it will cost about 20 seconds to ...
1
vote
1answer
122 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 ...
1
vote
2answers
5k views

What is the “-nolisten tcp” parameter for X

I have just found that my latest kubuntu comes preconfigured with the following: in directory /etc/X11/xinit there is xserverrc #!/bin/sh exec /usr/bin/X -nolisten tcp "$@" But the -nolisten tcp ...
0
votes
0answers
15 views

tcp sesssion duplicate acknowledgement and retransmission

Please help in understanding why the receiver keeps sending duplicate acknowledgement yet the senders keeps sending old packet sequence (re transmitting of old packet seq)
0
votes
2answers
338 views

If there are 2 NICs on the same machine, can a TCP client on one NIC connect to a TCP server on the other NIC?

I use TUN/TAP to create a tun NIC tun0 with IP 10.10.10.2, and I have a real NIC eth0 with IP 202.112.34.49 Then I run a TCP client which binds its socket to 202.112.34.49 and a TCP server binding 10....