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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How to run wireguard over tcp with udptunnel?

I'd like to run wireguard over tcp. I wanted to use udptunnel for sending udp packets over tcp. However, when I run wireguard and then try to run udptunnel, the udptunnel fails with the following ...
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TCP communcation - HyperV virtual machine opening port on host

Here's the summary of my fight to connect to a port on the hypervisor host from a VM hosted on the same machine: Set up in the Hyper-V Manager: Virtual Switch Settings Internal 'Enable virtual LAN ...
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TCP Reno over loopback linux

When I increase delay to 2000ms and loss to 3%. I received corrupted file on server(1MB file is sent from Client to server over TCP Reno). Why could be possible reason for this? And when I send small ...
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WebSocket connections originating from local network all use same client-side port (instead of ephemeral) when connecting to local webserver - Why?

I set up a webserver on a virtual machine on my home desktop. I have my router forward several ports (80, 443, etc) to my desktop, when then forwards them via NAT to the virtual machine (see diagram ...
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How to port forward UDP though SSH

I have a setup where I'm forwarding port 5000 to a remote server with ssh -NR 5000:localhost:5000 root@server This only forwards TCP packets through the SSH tunnel, Due to new software which is picky ...
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connecting with external ip is extremely slow

To be clear, I am an extreme noob when it comes to networking, so please be kind. It takes an exorbitant amount of time to connect to my server (running on my home network) with an external ip (domain ...
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How to emulate a keystroke with a special network data packet?

I'll start from far away. There is a mixing console that is connected to the router, the router is connected to a computer (local network) The mixer has its own IP in the local network. This mixing ...
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Increasing connection timeout for tcp connection in freebsd after 360sec has no effect

Test Setup Configured a firewall to drop connection from a remote address IP address : 'yy.yyyy.yyyy.yyy' IP port : 'zzzz' [root@mmmmm /path/to/log]# cat ipfw.today 00100 1438 86280 deny ip ...
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Low-traffic network retransmissions and fails

I have an local network with generally very low traffic. On the network I have oscilloscope with LAN access, which I want to interrogate. When downloading samples (which come in blocks of a few ...
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How to calculate effective throughput from link speed, packet loss (%) and delay information?

I am working on a networks assignment where two linux VMs (say client and server) are connected by a bridge and I have to use ftp (vsftpd) to send a 100 MB file from client to server. I have set the ...
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TCP Packet drops on application server

I have a monitoring application (Zabbix proxy) installed on RHEL 7.8 and since we have a very large environment, we have 2500+ agents connecting to this one server. We're seeing frequent errors while ...
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How to allow only 100 half open SYN connections

I'm running Ubuntu and want to allow only 100 waiting SYN connections at a given time, and drop the rest. How can I configure iptables to implement this rule? Or sysctl config to allow only 100, and ...
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MacOS Time-machine lots of TCP Window Updates and TCP Dup ACK: sign of problems or just normal behaviour?

I was recently investigating reported packet drops on my NAS (reported by netdata). While capturing the data a Time Machine backup was running and I saw a lot of TCP Dup ACK messages. In between where ...
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Using iptables, how can I redirect a port so that incoming requests bypass other reject rules

I have a machine and its access is secured using iptables. Only a defined list of ips are allowed to access the application which is listening on port PortA. I want to open a second port, PortB, which ...
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Increase buffer size for a specific socket on Linux

I am using CentOS7 and I have to increase the send buffer size (SO_SNDBUF) on a socket listening on a specific port. The application that has the port opened does not natively support this. Few things ...
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Create virtual serial port (COM <-> TCP) via terminal on Windows 10

Context I am working with a module built around a headless Raspberry Pi CM3+, the only form of interface with which is an ESP8266 chip (bear with me, the question isn't about either of these) which is ...
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Modbus TCP Corrected Message

I am using freemodbus library for the stm32 modbus TCP client example. But I want to learn how to protech modbus tcp message on the line. For example Master wants to read 5th holding register from ...
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What would prevent a TCP server port (once closed), from being re-opened right away?

I have a server program that uses TCP. Sometimes, I need to restart the program for updates, or any other reasons, but when I do, the program closes the server port, and then once it restarts, it ...
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QEMU: SYN/ACK ignored on host in host-only networking with tap interface

I'm trying to set up host-only networking between my Linux host (running Fedora 33) and a QEMU instance (a fork for Xilinx devices), more specifically between a bridge interface (host) and a tap ...
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Are we still limited by TCP Windows Scaling when we want to fully utilize download speed from far away servers?

According to this website, as soon as round-trip time is increased, we lose a bit of our real-time capacity throughput to distant servers using default TCP Window size of 64KB. My network bandwidth is ...
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socat resetting USB port on open

I'm having an issue with socat, and it is probably just in my environment. I need to have a USB serial port redirected to a TCP port. I use the following and it works perfectly: socat TCP-LISTEN:4444,...
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Configure openvpn for ExpressVPN TCP ports

I want to use the openvpn client on my Ubuntu 20.10 to connect to ExpressVPN's VPN. Unfortunately I have to use the TCP ports, as the UDP ports are blocked. ExpressVPN's website only allows to ...
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SSH file transfers slow with lots of TCP retransmissions

Good evening, I use SFTP (File Transfer over SSH) from a computer (Windows 10) to a Synology NAS. Both devices are behind NAT on different locations. Around 3 weeks ago, whenever I initiated a ...
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Basic TCP Connection

I am trying to use basic TCP-IP communication with two different stm32 devices, one of them TCP client one of them TCP server. On the wireshark picture; Up to the arrow mark both client and server ...
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Why do I get a “TCP Retransmission” right after having sent a packet?

I have a program (in Python) that publishes information to a bus (MQTT, implemented by mosquitto). This is a "fire and forget" kind of message, that is there is no long term subscription, ...
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After opening port 443 in windows firewall as inbound rule, I cannot see it when I run 'netstat -an'

As an inbound rule on Windows 10 firewall, I added port 443 as TCP connection allowing all types of connections. However, I cannot see it when I run 'netstat -an'. How can I get it so that I see my ...
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TCP port number reused

I am using STM32 TCP Echo server client Cube IDE example. I have server and client device. I can connect first time successfully but when I reset the client, I get after 70 line in wireshark ...
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Chunked HTTP response does not come through completely

Consider the following setup +-------+ +--------+ +----------+ | | | | | | | +----------->+ +---------->+ ...
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TCP Modbus Remote Port

I am using freemodbus library for stm32f4 for modbus slave device. I have a problem with Modbus TCP remote port connection, When I powered up slave device, and connect to Modbus master PC than they ...
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TCP Master and Slave Socket Open and Close

I have two device one of them Modbus master and another modbus slave.Modbus master working on windows PC. And it polling modbus read query and expects modbus response. They communicate succesfully ...
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Modbus TCP Master-Slave

I have a problem with modbus master and slave TCP communication, On windows computer: When Master and Slave connect each other they communicate successfuly on 50905->502 ports, when I disconnect to ...
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How does the server get the correct MSS value in the TCP triple handshake

When the client establishes TCP connection with the server, it will report its MSS value during the third handshake. According to my understanding, the MSS value should be obtained by subtraction 40 ...
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is “Empty reply from server” a deliberate reply, or a default one from the TCP/IP stack?

I have a device whose port 80 is open and I was wondering what is behind: ~ # curl -v http://192.168.10.253 root@srv * ...
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Why HAProxy tcp-request content do-resolve is not working

i am using a combination of HAProxy (docker image v2.3.2) and Hashicorp Consul (v1.9.1) to access my VMs behind haproxy using SSH (i followed https://www.haproxy.com/fr/blog/route-ssh-connections-with-...
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VMware VM client (Windows 2016) IP disappear for a few seconds

I have a Windows Server 2016 VM sitting on a VMware host (hosted by my local service provider which I have no access to). Everyday at 5am our application will restart on schedule, but recently we ...
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Relation TCP acks and MQTT acks

Is it somehow possible for a MQTT client to receive an MQTT PUBACK message without having received the TCP ack? for example: The client publishes a message with QoS 1. The broker receives this message ...
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java.exe opens up hundreds of ports on 127.0.0.1 on a windows 10 computer and listens to itself

After I ran netstat -ab with admin right on my win10 computer, which is not running anything "java" related on the desktop nor there is "java.exe" in taskmanager's "detailed ...
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Disable instant closing of TCP connections when interface or route becomes unavailable in Windows

Whenever there is a brief glitch with my ethernet connection, Windows 10 instantly closes all of my TCP connections going over that interface. Is there a way to change it so that the connections are ...
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Exporting TCP Connection Latency in Resource Monitor

In Resource Monitor in Windows 10 I am looking to monitor and log out the latency of for a particular TCP connection. In Performance Monitor there is the option to create a data collector set but I ...
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Log a TCP stream so it can be opened in Wireshark

I have an application that opens a TCP socket and sends and receives some data binary data. I would like the application to be able to log the sent and recieved data into a format that can be opened ...
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understand ss -to4 output for a jdbc connection

My application connects to a database over JDBC, and performs a lot of sequential inserts. There is only 1 JDBC connection opened by the application. As the performance is not as expected, I started ...
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How to set different TTLHOP for TCP ports

We want to set sensitive TCP/UDP Ports at low TTL/HOP Leaving other ttl/hop at 128 default data center = 3 Priv net = 8 Internet = 128 default Ssh 22 = 8 (internal hop max) Rdp 3389 = 8 Http 80 = 128 (...
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How to diagnose blocked TCP traffic on wireless network

My home wireless network has been having intermittent issues where the TCP traffic out appears to be blocked. UDP traffic is seemingly unaffected (can do dns lookups, if on VPN the connection stays ...
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Troubleshooting transport layer connectivity issues with pfSense

I am building a virtual network of vhosts that is NATed out to the internet through pfSense. For some reason, vhosts cannot establish connections to the outside world, although lower-layer operations ...
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What are AI_V4MAPPED addresses used for?

I found an odd network configuration on an old RHEL 5.8, hosting an Oracle DBMS. The line I don't understand is the one concerning the address:port ::ffff:127.0.1.1:1521. I never saw that before. I ...
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Sniff tcp connection and forward to TCP connection on other adapter

I have a system with two network adapters. One of the network adapters is connected to a port mirror, so it sees all the traffic in the network. I'd like to sniff that connection for a certain TCP ...
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Traceroute/tracert fails to receive hops return information

I noticed that with some routers/gateways when I issue a traceroute or a tracert in a 'inner' computer the hops always fail with: request timed out can anybody clarify this? what information goes ...
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Assigning IP addresses manually

I have internet connection from a local ISP at home. I see other routers and their IP addresses on my network using wireshark, when I connect the ethernet cable from ISP directly to my laptop using ...
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How to adjust TCP Window Size?

I've searched the web, followed the instructions and failed. The resources I had found were rather old. At this point I think it is appropriate to ask this question here. I don't really have any ...
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How can I stabilize my wireless internet connection if it keeps dropping?

My current internet connection is very unstable. I'm using a Windows laptop connected to a 4G smartphone's Wi-Fi hotspot. The 4G signal is often so weak that it disconnects my phone from the network ...

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