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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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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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How to create persistent TCP connection “proxy”?

I need to create some kind of TCP proxy to maintain persistent connection from one side. CLIENT --[persistent]--> MY_SERVER --[reconnect]--> THIRD_PARTY MY_SERVER should maintain persistent ...
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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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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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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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57 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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74 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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19 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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129 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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82 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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66 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
120 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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73 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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21 views

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
31 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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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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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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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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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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28 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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59 views

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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134 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
35 views

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 ...
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1answer
360 views

What means “Communication administratively filtered”

I am facing a problem in a foreign country reaching a special server per TCP/IP. ICMP is no problem but it looks like the dialup access provider is somehow filtering the TCP port 25 (SMTP). I get a ...
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303 views

TCP spurious retransmission and duplicate ACKs for Virtualbox guests when bridged

Using Virtualbox 5.2.8 on Windows 10 Pro 64 Bit I noticed that sometimes TCP connections stall. The guests are Linux (various distributions). When I investigated the issue I found that this happens ...
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1answer
58 views

What are network ports internally? [closed]

I know there will be multiple ports in the host/computing machine for each of the services that i hosts on the network. But i want to understand what are these ports internally? Below is my ...
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4answers
684 views

How to send binary data in netcat to an already established connection?

I can do the following to send binary data in netcat: echo -e '\x80' | nc host port But I don't want to do it like this, what I want is to connect to a server: nc 192.168.1.115 12345 And then send ...
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284 views

How to make tcpdump display only source IP, destination IP, ports and timestamps

I am running tcpdump to track traffic on 2 interfaces, one input and one output. The sole purpose is to measure the latency between the time when the input interface receives incoming TCP traffic and ...
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RST hijacking good ACK number

I'm trying to perform a RST hijacking sur on my Virtual Machine. I have 3 Vm's: -attack : 172.10.10.11 -victim : 172.10.10.21 -pirate : 172.10.10.31 First, I connect from attack with telnet to the ...
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TCP Selective ACK (SACK) never works and Delayed ACK (DelAck) only occasionally works on inbound traffic, but OS is configured to support both

Performance graphs from Windows Performance Monitor show that: For all Internet connections tested only except my ISP’s speed test page, the number of segments sent (nsend) ≈ the number of segments ...
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How many connections can OSX support?

I'm using FTP software and it has an option of using 1-30 connections for uploading. How many connections (internet) can an operating system like OSX make and how do I know what value to choose? I ...
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1answer
84 views

Can I bypass layer 3/IP to send a TCP packet?

As I know We can just use a Ethernet/layer 2 address to communicate with LAN device. But for a WAN device IP/layer 3 address is required. so TCP is in OSI 4th layer above IP layer. my question is can ...
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1answer
67 views

sudo netstat -antp not showing PID

i am testing stuff with sockets and i encountered that strange case : i coded i very simple tcp server in c, i made it block after accept(), just to see what happen when accepting multiple connection ...
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1answer
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identify individual devices from aggregate traffic of router

Is it possible and if yes how to identify individual devices (laptop vs. mobile phone vs TV) when listening to the aggregate traffic of a wifi router? Assumption: all devices of interest are ...
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Conntrack doesn't show packets and bytes

I am trying to use conntrack, on Centos 7 (kernel: 3.10.0-693.el7.x86_64) to monitor TCP connections with this command: conntrack -L Which seems to work fine: tcp 6 299 ESTABLISHED src=10....
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2answers
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Cannot make a TCP connection on private network

I am testing the local connection between two OS X computers using netcat. They are both connected to the same router (through wifi) and have the same public IP, so I believe they have access to the ...
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1answer
173 views

How to make a port listener code in the server that hosts my website?

I have my website hosted in godaddy, and I want to test one of the Embedded Application's TCP data transfer using the IP and port number of my website, for this can I use any php script (something ...
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1answer
55 views

Wireshark - what happened?

This Wireshark issue has been driving my crazy for a few hours. What's happening here? 192.168.2.100 is an Apache server that is serving a static file. 192.168.2.196 is an embedded client ...
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424 views

Disable TCP SACK option

My question is about How can i disable Selective Acknowledgment (SACK) option in windows server 2008 . How can i know its status on the server if it's enabled or disabled . Microsoft hot fix It ...
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334 views

Use netcat to Convert UDP DNS Queries to TCP DNS Queries

I'm running Debian 9 on an isolated network and need DNS services to resolve external hostnames. (I'm sure some will wonder why I need to be able to resolve external hostnames if I'm on an insolated ...
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Clients in LAN can't see each other

We have 2 windows 10 PCs sitting next to each other plugged into the same router (Fritz!Box). They are both on the same network mask 255.255.255.0 and both clients have the windows firewall disabled. ...
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117 views

Port is filtered by nmap

Long story short: I have opened a port one computer and I'm trying to access it from other computer in different network. It's failing. Details: I have 2 laptops: A - Ubuntu 16.04, firewall off, ...
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124 views

Data rate per connection in Transport Layer

In a network that has a maximum TPDU size of 128 bytes, a maximum TPDU lifetime of 30 sec, and an 8-bit sequence number, what is the maximum data rate per connection? My attempt: in 30 sec we can ...
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54 views

Broadcast on multiple interfaces under Windows 10

I'm using ZeroMQ socket (bound to tcp://*:12345) to publish messages on multiple interfaces. This works fine as long as the interface isn't a USB-bound device using IP passthrough. I'm not capable to ...
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100 views

How to optimize tcp stack for low latency when throuput is not a priority?

I have a wireless link with packet loss of up to 10%. It has to carry one rtp stream, nothing else. Datarate of the stream is <100kb/s so the lowest datarate offered (1 mbit/s) by wlan (802.11b) is ...
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1answer
127 views

Difference in network utilization between single and multiple TCP connections

We know that the way (basic) TCP works is by starting with slow-start phase followed by a linear increase of congestion window (CWD). The CWD is adjusted according to network status. So once we ...
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Windows 10 always denies tcp connection

I have windows 10 x64 os. I have Kaspersky Internet Security 2016 installed. Recently, I noticed that connections leading to localhost or 127.0.0.1 or ::1 is being rejected. I have tried exiting ...
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114 views

How to send only single TCP RST with TCPKill

Is there a way to send only single TCP RST packet with TCPKill when application attempts to establish connection, e.g. on port 54321. What I want to test is a custom implementation where application ...