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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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Shall syslog be used with udp, tcp, or tcp over TLS?

Of course, it depends the usage: UDP port 514 has been used by sysadmins for years to monitor IT mostly for performance, usage, maintenance. Loosing some logs was not important to get the whole ...
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Linux doesn't close TCP connection after change a Wi-Fi network

There is some TCP connection between some device behind NAT (Wi-Fi router) and server, located in Google Cloud, both under Ubuntu 16.04. When I changed a Wi-Fi network, this device keeps this ...
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802 views

Use netcat to tell a remote Mac to run/open a file

I have very limited (almost no) knowledge of how netcat works other than I've managed to get one Mac mini to listen on port 13370 [using nc -l 13370] (for TCP commands?) and I have a MacBook that has ...
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1answer
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OpenVPN via TCP or UDP

I read a question here about this topic but actually I am not super sure whether I understood it correctly. Unfortunately, because of my low reputation I can't comment there, so I decided to ask here ...
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1answer
42 views

Why are initial connections always slower

I first noticed this when using Insomnia (HTTP clients) to test some of my API endpoints. The first request I make to my API server (and others) is always 100ms+ but sequential requests are always ...
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1answer
12 views

Delay a tcp stream [closed]

I need to synchronize two different streams of data. I'll call them strem A and B in the following. At time zero, both streams start from the sender. But stream A suffer a delay at the beginning of ...
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26 views

TCPView Chaos due to Google Chrome

Since using Chrome with TCPView I've noticed the browser opens many, many processes each of which only sends a small amount of data before closing. This spams the out put window with connections on ...
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54 views

Slow TCP/IP and UDP communication

I am working with a device on a metal cutting machine that communicates using TCP/IP or UDP over Ethernet. I wrote a test program that writes and read ten registers and times how long it takes for the ...
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Is using a dynamic port a good solution to software-test servers?

For testing (automated, TDD, ATDD/BDD, also running on a CI/CD pipeline), I want to run a server on a dynamic port. The test shall start the server, perform tests, stop the server. This shall be ...
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20 views

tshark: using frame contains and write to file

i want to filter out TCP packets that contain a specific string in the frame data (data.data) tshark -i 1 -f "tcp port 8800" -Y "frame contains FILE" -w "data.txt" This is exactly what i want. ...
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Accessing IPv6 Only Network from IPv4 Network?

My ISP has provided me IPv6 only internet connection. If I connect from my IPv6 PC to IPv4 Internet I have no issues, because the ISP does all the IPv6 to IPv4 conversion. However, at home, on this ...
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1answer
61 views

Safely perform TCP traceroute from user request

I need to perform a TCP traceroute using either the Linux traceroute or another package, but I'm struggling to find a way of making the request from PHP without needing sudo privileges. Because the ...
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1answer
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Checking Nagle Algorithm on opened socket

One of the platforms we use opens TCP sockets (No source code available). I need to check if the Nagle Algorithm is disabled or enabled on those sockets. The operating system used can be Windows or ...
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72 views

Why is my TCP connection attempt via PHP acting weird?

I'm not sure if this is better here or on SO but since the issue isn't in the programming I figured it applies here (or on U&L or on serverfault, but I guess/hope I'm fine on here). I want to ...
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1answer
70 views

Wifi-Lan Port blocking

I'm writing a paired (windows) server and (android) client application suite that uses TCP connections over wifi on a funny port number. The Server advertises its availability using Bonjour/Zeroconf. ...
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1answer
126 views

why can't we just upload a file and it reaches its destination without the other device downloading it? [closed]

when we have to view or get some content off the internet. We have to download it on the other hand the server uploads it So here's my question => Why can't the server simply upload the file and it ...
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1answer
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Does HTTP as a protocol include any mechanism for guaranteeing information?

I asked this question on networkengineering.stackexchange, without realizing that any protocols on top of TCP were off topic (i.e. that only OSI layers 4 and lower are on topic there). The question ...
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1answer
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Does a remote TCP Server has to run on Public IP address only

I have interfaced a GSM (Uni4 SIM800) module to a Raspberry-pi-3B module using AT commands to run a simple TCP server, and another pair of GSM and Rospberry-pi to run a TCP client. Now the Telecom ...
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1answer
33 views

VPN not connecting to a specific site

I've been using NordVPN for quite some time, but sometimes when the VPN is on certain websites become unreachable with a timeout error. For example, https://g1.globo.com is only accessible when the ...
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Does TCP Nat hole punching requires both router to support

I've heard that TCP Nat Hole punching only support some type of router. For example ZyXel won't support TCP Nat hole punching while Linksys support it. What happened if I try to connect between a ...
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1answer
138 views

Getting a UDP-only VPN to work over TCP

For a project of mine, I'm searching for possibilities to have a UDP-only VPN working over TCP (preferably on port 443 or 80). I have found the following while doing some research: This is possible ...
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95 views

Changing the TCP initial congestion window value in Windows 10

I would like to do some testing with the TCP Initial congestion window on Windows 10 Pro, but it seems the settings are disabled in the Pro version: Set-NetTCPSetting -SettingName InternetCustom -...
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Frames above 2000 bytes not acknowledged by the client/receiver

I working on adding a jumbo frame functionality to my application. My problem is that I receive no ACK for frames with payload above 2000 bytes. My system looks as follows: the server sends requested ...
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Need help figuring out a random connection timeout issue on a server

I discovered this issue trying to loadtest a custom node.js websocket server, where some sockets are failing to connect (they hit the connection timeout). It does not appear to be related to the ...
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1answer
46 views

Short description of the difference between TCP and IP [closed]

I am learning about TCP and IP but there is a lot to each of them and it will take a while to organize the concepts around them. I'm wondering though if one could briefly describe how TCP and IP ...
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TCPView: [System Process]

In TCPView I get a lot of connections listed under the Process column as [System Process]. These connections cannot be terminated, and cannot be whoised. How can I find out what programs started ...
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RTSP - continue recording after network issue

I have a problem with capturing RTSP stream over TCP from IP Camera. I tried many options like timeout, stimeout, other flags related to key frame etc, nothing helped. FFmpeg is capturing stream ...
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110 views

Changing the TCP Destination address using WinDivert or PyDivert

I'm trying to "route" TCP traffic by using WinDivert to change the Destination Address (and port) of certain outbound traffic. I began with using PyDivert as I am a total and complete programming ...
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151 views

TCP traffic not working through Iperf tool in ubuntu

I am using system-A(interace name:tun0; IP: 192.168.3.1) and system-B(interface n ame:ss200; 192.168.3.2) which run on ubuntu. When I try sending traffic in TCP mode from A to B or vice versa, by ...
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1answer
83 views

Practical (vs theoretical) max limit of TCP packet size

I'm a web developer who is pretty new to the industry. I was presented with a coding challenge for a job interview where I need to design a messaging system and architect a system for how it deals ...
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1answer
457 views

TCP reset (RST) flag

I am trying to stream a video between 2 hosts also I am trying to simulate changing IP scenario, the client started listening to the server then I moved the client to the new switch and it is got 192....
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379 views

netstat Foreign Address shows my hostname, TCP sockets refuse connections

I am attempting to establish a TCP connection to a Windows machine running some third party software, unfortunately, I can not make the connection succeed. Running: netstat -an Shows my service is ...
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22 views

HTTP Video streaming failed because TCP re-transmission

I am trying to stream a video between 2 hosts but I am trying to simulate changing IP senario by listing to an IP (192.168.2.3) instead of the real IP(192.168.2.5), I am using mininet and Ryu ...
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805 views

How to immediately kill orphaned TCP connection?

Closing orphaned TCP connections is surprisingly difficult in Linux. This issue has been raised here, here, here, and here; however, neither of the approaches worked for me. Calling close() doesn't ...
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1answer
116 views

how to open tcp connection in fish shell

I am looking for a way to open TCP connections in fish shell. In bash, I can do the following to open a TCP connection. This is quick telnet type test when telnet is not installed. $ echo > /dev/...
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2answers
224 views

How to use nc to listen on a TCP port indefinitely?

I want to read the data arriving on a specific TCP port indefinitely and dump the data into a file. I have tried many different variations of nc but it is not working out for me. For the most part I ...
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1answer
250 views

Which protocols (TCP or UDP) consume more %CPU?

I'm sending data from the client to server using IPERF3, fist I used TCP and then UDP. I observed that maximum time TCP consumed more %cpu than UDP. Generally which one suppose to consumed more %CPU? ...
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Can't stablish TCP connections into a Hyper-V Centos VM

I've set up an internal network with a VPN gateway on Hyper-V on Windows 10. It works fine in the sense that all VMs can communicate with one another and with the external world. The problem happens ...
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1answer
77 views

OpenVPN doesn't forward HTTPS traffic, HTTP works fine

I have an OpenVPN server running on a Raspberry Pi, and I'm encountering issues trying to connect to HTTPS sites using it. I can connect to HTTP sites (confirmed via nc example.com 80). From the ...
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Cannot Connect With PC Which Is Using VPN Through TCP

I am working on simple client and server program to make communication between devices. The scenario is: PC1: This PC is running server version of program. This PC connected with Internet (...
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1answer
34 views

How to configure OS to re-assemble TCP segments

I have an application that is reading in TCP data from a socket. The sending device is sending out a full 1400 bytes of data to the server's socket on the other end. Somewhere along the way, the ...
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25 views

Why TCP scan is more reliable that SYN scan?

I heard that the TCP connect (-sT) scan in Nmap is much sure than the TCP SYN (-sS) scan. But why ? Does the TCP SYN scan generate false positives which is not the case for the TCP connect scan ?
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1answer
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Port forward traffic from restricted network with home unrestricted

Here is the scenario: I have an enterprise e-mail whose SMTP server listens on port 2525. I can configure an e-mail client like thunderbird in my home without any problem. I also have another job, ...
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35 views

in Debian server, IPTABLES PREROUTING behave differenty for different ports

I have following three rules in my iptables firewall -A PREROUTING -i eth0 -p tcp -m tcp --dport 12346 -j DNAT --to-destination 11.207.2.4:12350 -A PREROUTING -i eth0 -p tcp -m tcp --dport 12348 -j ...
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0answers
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How do I make ppp reliable over lossy radio modems using pppd and tcp kernel settings on debian? [closed]

I am having a lot of trouble establishing a reliable ppp / tcpip link between two debian systems over radio modems. My hardware topology is a little complex. The system uses: Raspberry Pi 3B at ...
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30 views

TCP sessions limit over bridge mode

I have an iDirect satellite modem (X5) which is limited by only 1500 TCP sessions and it doesn't support bridge mode, but they have other modems that support it that I could purchase. My Question is, ...
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What is TCP's three way handshake response to old connection?

Lets say we have two hosts (A and B). How does the three way handshake process prevent a old SYN-segment from A to connect to B. It starts with A sending a SYN to B, and then B responding with?
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163 views

Destination Host Unreachable between linux boxes

I have a home wifi network with 2 linux and 1 mac system. I can reach each linux from mac and other way round, but an attempt to ping a linux from another linux results with "Destination Host ...
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1answer
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tcp session - http request [ x out of y] in wireshark capture

As below, i am seeing this [HTTP request 1/2] and [HTTP request 2/2] in 2 separate payload, are they separate GET request in a single tcp session or are they the same GET request ??? ==== Added full ...
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1answer
24 views

Redirect with a port

We want to launch a little Minecraft server community, With one server for a forum, another for the Minecraft server. I know how to make a subdomain for the MC server but what I want is to have the ...