Questions tagged [tcp]

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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buffer deadlock prevented error from RTSP streaming over UDP

I have an issue to view RTSP streaming over UDP in the open VPN connection. Our project is to integrate 360 degree IP camera in unity system. And we want to get the UDP streaming rather than TCP to ...
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network connection works only once

I have setup a home server and did port forwarding for http/ssh/tcp etc on the router. It was working well until very recently. My problem is that now connections seem to work only once from outside ...
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Due to pandemic has caused increase in network usage as more people start to work from home, How does ISP handle this situation? [closed]

what can be done to TCP to help capacity bottleneck? Can removing TCP and only sticking with UDP helps, if not what else can be done?
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Packet reaches OS but not the process

Sorry if my issue is a bit hard to summarize in the title. That is the best I could come up with. TL;DR Version: How do I debug when packets reach OS, but not the destination process? Explanation: I ...
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Network subnet completely blocked by laptop (external ethernet dongle)

This has now happened to me multiple times. In the most recent outage the Internet went down (the cable modem started returning a local IP address instead of the external one) which I don't believe ...
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Client not sending ACK packet in response to SYN-ACK

I'm seeing a weird network behaviour with my TCP 3-way handshake in my home lab. Setup is from my Windows 10 host on one network, through pfSense, and into an Ubuntu VM on a different one. Firewalls ...
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How to enable ECN marking in IP header in Linux?

Is the ECN marking in the IP header is performed by default in Ubuntu (4.15.x kernel) or should the kernel be recompiled with a special option? I configured a RED ingress queue at an Ubuntu machine, ...
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ssh tunnel to forward ports to a virtual machine running in the cloud

I have got a network device (running linux, I have got no shell access to it) which is connected to my local network. In addition to this I do have a Windows application running which interacts with ...
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Utility to display received TCP data

I'm writing code that consumes a TCP protocol - no authentication you just connect and wait for data. I'd like to display & save this data nicely formatted - e.g. hex - and before I waste time ...
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When connecting via SSH, does the Diffie-Hellman key exchange take place over an unencrypted TCP session or does encryption occur before the exchange?

I'm a cybersecurity student and I'm eager to understand the basic processes of an SSH session. I wrote down the stages to the best of my ability, but need help understanding what happens right after ...
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Will Windows 10 Proffessional allow to listen in more than 20 ports from internet

Windows 10 license allows no more than 20 connections for some ports: (iii) Device connections. You may allow up to 20 other devices to access the software installed on the licensed device for ...
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TCP RST when connecting via telnet to the application - Windows

I have an application running on Windows. The application listens on port 54000. I can connect to the application from the local machine and it works fine: telnet 127.0.0.1 54000 Now, I am trying to ...
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How can I know what is preventing my socket to bind to localhost:50060-50959

I am using this Python code to listen to a port on my Windows 10 system: import socket for port in (50059, 50060, 50959, 50960): try: print(socket.socket(socket.AF_INET, socket.SOCK_STREAM)....
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Capture only TCP SYN-ACK packets with tcpdump

I'm trying to capture only TCP SYN-ACK packets, i.e. with both SYN and ACK bits set with: tcpdump -vvvni eth0 tcp[tcpflags] == tcp-syn and tcp[tcpflags] == tcp-ack but it gives such error: tcpdump: ...
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What is TCP over SSL [closed]

There is this application called "TCP over SSL Tunnel". In his office, he only has access to education sites through the internet. He is using this application and connects to an accessible site over ...
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TCP ping output explanation?

I ran a TCP ping from my Windows PC to google.com and following is the output : I was reading this thread to understand how TCP ping works and it mentions that a "half open scanning" is performed ...
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Ways to establish TCP connections between 2 computers that are located in remote networks behind firewalls

I'm trying to implement persistent TCP connection between 2 machines. They are located in different networks behind firewalls, so there is no way to establish direct connection I'm trying to figure ...
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What address type do DNS queries use?

I was reading this thread and it was mentioned that DNS servers use anycast address. I have also heard that there is something called Unicast DNS as well. So, my question is what type of addresses ...
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Do socket and buffer mean the same thing?

I think my question is fairly clear. I was reading this article to understand how sockets work, and it mentions the terms socket and buffer interchangeably : Assuming the packet is in sequence, the ...
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How do Flow Control and Congestion control work together?

I am trying to learn about Flow Control and Congestion Control in TCP. So far I understand that flow control uses the sliding window method and the receiver advertises a receive window based on how ...
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How is network congestion detected in TCP?

I am trying to learn about Congestion Control in TCP and in this video (at 1:56), he says if there is no ack received, it assumes network congestion and cuts back the cwnd, no where he mentions about ...
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What is the initial value of ssthresh?

I am trying to learn about Congestion Control in TCP and I understand that there are two modes of operation - slow start and congestion avoidance. When the value of cwnd > ssthresh, the congestion ...
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When is the TCP receive window advertised?

I am trying to learn about the TCP 3 way handshake and flow control. I was reading this and I understand that in the 3 way handshake the sender and receiver agree on the Sequence and Acknowledgement ...
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Port forwarding stops working after a while

Second day in a row I am having a hard time setting up port forwarding on my mac. I was working on a micro service and wanted to utilize through web. I might have messed up some settings, because a ...
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Unable to connect to FTP server from AWS instance

We used to connect to FTP server( client's other server) from our AWS (ubuntu) instance. But all of a sudden we are unable to access that ftp server from our AWS instance. There is no credentials ...
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TCP connection closes instantly (without timeout) when I change my IP address through the windows network and sharing center

I have tcp connection to some tcp server on internet. Tcp client is a simple application that I have created which works on my computer. The problem is that when I change my ip address through the ...
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Why are DHCP messages broadcast?

I am learning DHCP in my networking class and as a part of my research, I was watching the following video: https://www.youtube.com/watch?v=0UvLRVlPx6A So in the Wireshark capture in the above video ...
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Why do most application protocols have two ports assigned?

So I am trying to learn about the application layer in the OSI model and when I go to the IANA website, I notice that most of the well known protocols have same port assigned for TCP and UDP. For ...
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Real world example for PSH flag?

I am trying to understand the difference between the TCP PSH and URG flags. I know so far that when the PSH flag is set, the receiver device doesn't wait until the buffer is full - it just sends the ...
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Use netcat to listen on a port and send output from a command when a client connects

I have a Raspberry Pi (Debian Linux) connected to my LAN that can read data from some connected devices and output it to STDOUT. Let's say the program is run on "Server" and I want to serve the ...
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Telnet connection failing via port 23 (port is open on the server)

I have a Windows Domain controller and a Windows 10 Work Station set up from my VirtualBox. I am trying to connect to the Work Station on my domain via telnet on my Windows domain controller. It ...
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Is it safe to rely on zip to find data corruption in transmitted zip files?

In one paper I read that we can detect errors in the transmitted file by zipping and unzip, but I have doubts. For data integrity check, what if we do some operations before sending the data ...
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Why is Ubuntu server unable to send outbound connections?

I am trying to connect from a Ubuntu server to another machine (Windows or Mac, neither works). I am trying to test the connection by running nc -z -v my.ip.address.00 897, to connect from Ubuntu, to ...
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HAproxy tcp load balancer with IP src address and TCP src port persistence

HAproxy tcp load balancer with IP src address and TCP src port persistence I’m looking at switching from nginx to HAproxy (because the freeware version of nginx does not support layer 7 health checks)...
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Sending HTTP content over multiple TCP connections

Is it possible for an HTTP content to be sent over multiple TCP connections? If so, what fields indicate that this has occurred? I would assume partial-content?
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TCP speed stabilized and grow slowly

When I run multiple large file transfers over TCP (direction and upper protocol does not matter, it for example works similarly on HTTPS and FTPS) on Linux machine (but Windows works the same way) the ...
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Debian webserver ignores the syn request

Environment: I set up a Debian (v10) server with apache2 so I can host my website again. So that I can access it from outside, I have set up port forwarding on the router (port 8080). Problem: If ...
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TCP connection to a perticular application in redhat linux

I trying to make a connection between a particular cross tell application in my linux server to a remote linux computer to take data from that computer and process it on my server application. My ...
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Mac OSX: How to forward all outgoing traffic to specific host/port to different host/port?

I've been searching high and low for days and I'm 100% stuck with PF. Essentially I want to take all of my local, outbound traffic to ip/port redirect it to a different ip/port. local application ...
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CTF challenge. How to receive full flag using netcat?

Im trying to dip my toes a bit more into networking, pentesting etc and i might have a slightly vague question but i hope one of you are able to help I'm trying to poke at a CTF that were made by ...
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Seeing strange TCP retransmission traffic on smtp server port 25

I have been working on my postfix (and davecot) server and had wireshark open for debugging (and verifying that starttls was working). Now I suddenly started to get some strange requests from many IP'...
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Terminal application as a TCP server

I need to test wifi comms from a device under development. The device is set as a TCP client. I need a terminal application I can open in Windows 10 or in Linux that will serve as a TCP server with ...
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Convert Received TCP packets to UDP and forward those packet

I have a service that listens on a TCP port and communicates with a peripheral. I'd like to forward the received packets by the service through UDP to an another computer. I don't need handshake with ...
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will linux tcp purge the pkts in qdisc when do tcp_close?

when call TCP close(), should it purge the packets in Qdisc which has not been sent yet? Sorry, I can't find how to do this purge?
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TCP Reset Attack

I'am trying to implement a PoC for the TCP Reset attack. I am using 3 VMs(host A, host B and the attacker). Host A connects through SSH to host B. The attacker sniffs the connection between the 2 ...
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log the ende of TCP connection between 2 machine

I use Ulogd to log Trafic that pass over firewall. My Rule are in Forward Chain: chain FORWARD { type filter hook forward priority 0; policy drop; ct state established,...
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log tcp contakting connection with nftables

I Want to log TCP contracting Connexion using nftables(iptables) I tried to write tcp flags in Rule, but when I acces to webpage of destination IP address I get just this Info in my logfile : ...
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Windows and IISExpress with TCP keep-alive block further connections

I have a very annoying problem. During development of an embedded application with LwIP I have the server-side application running on my Windows 10 development machine so I can more easily debug the ...
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How to resume a file transfer using netcat or socat or curl?

I have to transfer a 400Gb database consisting of a single file over the Internet from a server where I have full control to an other computer at the opposite border of the ocean (but which uses a ...
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Is tuning linux TCP param has effect on active process

I have a mission to tuning tcp param on k8s deployed system, and I want to tuning it by k8s daemon set, which will auto deploy on every vm. So I want to know if tuning tcp params has effect on active ...

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