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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iptables reject tcp-reset on loopback

I am trying to check how a software would behave if there is a network failure. That software is using tcp send() and recv() to communicate. Previously I was making the software communicate by ...
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0answers
100 views

What is the full process of a client downloading a torrent file?

I'm attempting to write a torrent client, and while the unofficial specification is quite helpful on a technical level, I would like an explanation of the process of downloading a torrent file (...
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24 views

Download very large files with HTTP

I'm downloading the PlaceNet compressed database of place images (~132GiB). Unluckily the downloaded file is corrupted. I have tried several times, each time the extraction is stopped at different ...
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1answer
14 views

netem packet loss for packets destined to the same machine

I am using a command like sudo tc qdisc add dev eno1 root netem loss 10% to delay all the outgoing packets over the interface eno1, but this won't work if the packets are destined for the same ...
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0answers
61 views

How do I kill existing network connections on Linux?

I've been working on a project that is nearly complete: to be able to kill my children's internet connections at the touch of a button. I've implemented part of the solution by basically calling: ...
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16 views

Windows 10 tcp timed out

Few time ago my notebook with win 10 started behaving strange. My Google Chrome always give me ERR_CONNECTION_TIMED_OUT for something about 5 or 10 minutes and then start to work normally. I've also ...
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1answer
40 views

TCP socket buffer for every flow

Does the linux kernel create a buffer for every TCP connection, for example when we have 1000 tcp connections the kernel creates 1000 socket buffer and stores the packets of individual flow on its ...
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1answer
28 views

What are the default nmap options?

Which options are used by default, when the user fires # nmap target without any explicit option? I am going to write the defaults of the three options I consider the most important. It would be ...
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1answer
27 views

how can i get SYN & SYN+ACK value for current tcp connection of any website on Browser?

As I know that '$sysctl | grep net.ipv4.tcp' gives the system wide TCP parameter value,I need to make a script in Bash for my college practical file in which If we open Browser and input the ...
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3answers
117 views

Why do computers have 65,535 TCP ports? [closed]

Why do computers have 65,535 TCP ports? Where does this number come from? What does it represent?
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1answer
33 views

How get the value of TCP connection establishment timing,retry timing in ubuntu 14

how i get the value of TCP connection establishment timing ,retry timing for any TCP connection and also Quality of services parameters in Ubuntu .
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2answers
55 views

IPTables - Redirect traffic based on country

Is there any way how to allow TCP traffic only from specified countries on a specified port and the rest of traffic redirect to another IP/port using iptables ?
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1answer
38 views

Wireshark's reassembled PDU consists of TCP segment size > MSS?

I'm looking into a Wireshark record provided by someone, to analyze something for them. Wireshark has conveniently reassembled 3 TCP segments that all transported a single TLS packet. The TLS packet ...
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1answer
23 views

TCP connection with multiple proxies in between

Client sends an Proxy-Connection: Keep-Alive header, the intermediate smart proxy sees this header and replaces it with Connection: Keep-Alive and sends to the web-server. All good and fine. What if ...
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1answer
29 views

are TCP connections made while typing the URL

Do browsers make TCP connections while typing the URL in address bar? I launched nettop utility, and was surprised of how active my connections are, even while only typing an address and not visiting ...
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1answer
16 views

Tcp Re-transmission timeout in a very short time?

I have two Windows 2012 R2 machines (122 and 115) hosted on the same VMWare host. We have a heartbeat at application layer between those two machines, from time to time there will be tcp re-...
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0answers
23 views

Strange response from a HTTP server

I noticed an unfamiliar device when scanning my local wireless network. It had two open (listening?) TCP ports; TCP/80 (http?) & TCP/443 (https?). In an effort to identify the unfamiliar device;...
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0answers
17 views

Unable to find traffic for specific device w/ Wireshark (over Wi-Fi)

I have a device communicating with a TCP server running on my machine. My machine is normally connected to the network via ethernet, however I also have a wireless adapter that I can use to connect to ...
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0answers
15 views

Direct host SMB - Ports

It's well known that SMB uses port 445, and that NetBIOS uses ports 137-139. However, according to all official MS documentation (https://support.microsoft.com/en-us/kb/204279), SMB uses both TCP and ...
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38 views

TCP congestion control

I was curious to know which are the default TCP congestion control method used in latest version of MacOSx, linux kernal, windows 8, windows 7 and windows xp. Does it use newreno or anything newer?
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1answer
17 views

DrayTek Vigor 2830 open port issue

We're using a Vigor2830 for routing VoIP/SIP traffic. One of the ports required to be open is 5090 for TCP/UDP. Going into the open ports section of the Vigor menu we have opened all the ports ...
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1answer
10 views

Reason for TCP Slow Start in Subsequent Connections

From my understanding TCP slow start is used to compensate and prevent congestion and loss. When a connection is successfully established and used for a while, the bandwidth of the TCP connection is ...
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0answers
10 views

pfSense does not close connections coming from LAN

I created a NAT rule that redirects external_ip:1234 of modem (pfSense itself) to 192.168.1.100:1234. I also wrote a server application which listens for connections on 192.168.1.100:1234. When I ...
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1answer
84 views

Socat not closing tcp connection

I use socat 1.7.3.1-r0 and run following command on an alpine 3.3 linux server: socat -d -d -d PTY,link=/dev/ttyFOOBAR,echo=0,raw,unlink-close=0 TCP-LISTEN:7000,forever,reuseaddr Socat will listen ...
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1answer
14 views

Connecting from WAN to LAN

I'm developing an app for my family that uses sockets to comunicate between devices in LAN or WAN. As IP addresses change constantly I am planning an FTP server for address book and TCP/IP for ...
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2answers
30 views

TCP: Disable pure ACKs?

I have a scenario where I wish to disable pure ACKs (TCP ACKs with no data), but I can't find how to do this. Is there an option that I can set so that ACKs are always piggybacked onto the next data ...
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1answer
77 views

ping works but iperf3 doesn't show any traffic for TCP

machine A has IP (eth0: 192.168.1.1, eth1: 10.10.xxx.yy) machine B has IP (eth0: 192.168.1.2) A and B are connected through RJ5 on eth0, both sides. ping works fine on both side, but when running ...
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2answers
71 views

Why game latency fluctuates aggressively during day?

I play World of Warcraft (uses TCP) from India, on a server located in France. I get 180-200ms in-game past midnight which is quite comfortable for me, and unfortunately the best I can get due to the ...
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0answers
25 views

How to add latency to TCP packets?

I have tried netem and wanem neither seem to be affecting the TCP packets. How can I add latency to TCP packets?
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2answers
48 views

RST sequence number and window size

RFC793 states the following about RST processing: In all states except SYN-SENT, all reset (RST) segments are validated by checking their SEQ-fields. A reset is valid if its sequence number is ...
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1answer
38 views

Can two different applications bind the same port on a host if they use different protocols?

my question is quite clear I think. If two applications use different transport layer protocols (e.g. TCP and UDP or something else) can they open the same port number? How does the OS do the ...
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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)
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23 views

Duplicate and retransmission

Please help me understand why the receiver keeps sending duplicate acknowledgements, yet the senders keeps sending old packet sequence (re-transmitting of old packet seq) in the below capture: Please ...
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1answer
23 views

A bunch of tcp unseen segments and duplicates on wireshark?

Recently, my Mac has been unable to use the internet well. Even though it said my ping was between the ranges of 10-20 ms and my download speed was around 20 Mbps along with around a 10 Mbps upload ...
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1answer
38 views

TCP RST Connection - Netflix - Only on Linux

I wouldn't have asked this here, but I am at wit's end, this makes absolutely no sense at this point. I have been trying everything. I have a single iptables rule: -A POSTROUTING -o eth0 -j ...
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45 views

Drop resilient tcp tunnel

I'm looking for a tcp tunnel that can provide connection drop resilient TCP connections to my VPS. Currently when I have some tool connected to my VPS and I switch from Wifi to LAN or my internet dies ...
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0answers
178 views

No connection could be made because the target machine actively refused it

On Windows machine, I start a server on port 62325 $ netsh firewall show state shows: Ports currently open on all network interfaces: Port Protocol Version Program -------------------------------...
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1answer
79 views

Is it necessary for an RST packet to have an acknowledgement number?

I am studying about TCP reset attack. I know that some RST packets have an acknowledgement number (with the ACK bit set), and some RST packets do not have an acknowledgement number (the ...
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1answer
21 views

Acknowledgement number of an RST packet

This question states that the acknowledgement number of an RST packet should be 0, but I have found it to be other than 0 when I captured some HTTP packets using Wireshark. So when does the ...
2
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1answer
17 views

Can't get windows host file to forward HTTPS headers

I'm currently trying to write a proxy in C# using the host file to redirect requests (specific request). I only want it to intercept one address. It's on Windows and the proxy is run locally on the ...
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28 views

Still Lost on Blocking TCP Port Connections form Terminal

I'm still not 100% understanding what to do in Terminal to block certain URLs for specific ports. And I don't want to use Little Snitch. I really want to wrap my head around this. So if someone can ...
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2answers
120 views

Send TCP with incorrect checksums

I'm having trouble sending large files to an OpenStack machine. Our Internet connection is over LTE so bad packets are to be expected. However, even sending data over TCP results in corrupted data ...
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2answers
43 views

what distinguished OSI from TCP/IP in practice?

so i am going through cisco ccent/ccna. working through the text on my own just for general useful knowledge. so in the early part of the book it goes into describing the different layers of the TCP/...
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1answer
44 views

Close a TCP connection using nmap

I am trying to close connections in command line. For instance, I am trying to close my SSH connection with this Nmap command: $ sudo nmap -p 22 --scanflags RST <mySSHServerPublicIP> $ sudo ...
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1answer
21 views

Where do I start to troubleshoot this strange activity from my firewall?

I noticed that my firewall yesterday blocked outgoing attempts starting at port 61494 and worked its way up to 62381, making a TCP outgoing attempt at each port once. The remote IP address seems ...
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24 views

TCP and UDP do not work with firewall

I can not connect my TCP-Client to my TCP-Server. Here is my Code: http://stackoverflow.com/questions/35661591/tcp-server-does-not-work-with-firewall I have already opened my TCP-Port "8888" in the ...
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2answers
39 views

During queuing delay, do TCP, IP, and Data Link headers act as a packet or 3 different packets?

According to the definition from wikipedia, I found processing delay to be the delay caused by router processing the packet header. I am just wondering are TCP, IP, and Data link Headers all ...
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2answers
42 views

Why ICMP is different that TCP and UDP? [closed]

what is the difference between Internet Control Messaging Protocol over Transmission Control Protocol and User Datagram Protocol
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1answer
53 views

Can HTTP deliver video over the internet or is that TCP?

The post below talks about delivering video content to users via HTTP. Is it confusing it with the TCP protocol? https://torrentfreak.com/torrents-time-brings-popcorn-time-to-any-windows-browser-...
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63 views

How to simulate TCP simultaneous open and close conditions?

I am learning TCP/IP protocol. I want to see simultaneous open, close, half open/close, etc conditions in practice. I have created simple TCP server and client program. How can I simulate simultaneous ...