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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Improve connection speed for South America users to server in Europe
I'm running an MMORPG Game with central server based in Europe-Warsaw hosted on OVH.
My player base is located both in Europe (mostly Poland) and South America (mostly Brazil).
Due to server ...
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What is the name of the string that a service returns when you establish a tcp connection via telnet?
If you telnet to an ssh server, it will establish a connection and return a string, something like SSH-2.0-OpenSSH.... etc.
Something similar happens if you connect to a mysql server.
What exactly is ...
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Tuning Amazon Linux for TCP Handshake, receiving 200-300KB response, and then closing connection
I have an application which regularly creates a new TCP connection, makes a request, and then gets a just under ~300KB response before closing down the connection. Assuming that I can't redesign this ...
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Reusing client certificate for TLS proxy with nginx?
I have a TCP application that uses mutual TLS to authenticate connecting clients.
Because of increased traffic I'd like to clusterize the application and load-balance the nodes with nginx. I already ...
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[Send mail with attachment]: TCP Retransmission, Duplicate ACK => TCP Reset
So, we have a linux box with postfix running on LAN site A which sends emails to an Microsoft exchange server sitting on site B. This runs perfectly when there is no attachment to the mail. But as ...
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Unable to connect to local DB2 instance
I have installed an Enterprise version of DB2 on my local Windows 11 pro laptop for some development tasks.
Installation proceeded without errors but, it seems I cannot connect using TCP. If I try to ...
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nftables: Possible to block SYN packets with payload?
Is it possible to drop all TCP SYN packets with a payload using nftables?
The man pages mention various length options, but none that I could get to work for TCP packets without syntax errors.
I am ...
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TCP connect <--> accept with INADDR_LOOPBACK range
I have some production code for a distributed system. Part of this code works by looking up (already established tcp) connections in a hash table, indexed by remote ip address. This code works ...
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failure time out during tcp connection establishment stage
I want to learn VPX ADC in virtural environment. All the below 3 machines are connected via VMWare Workstation Bridged Network.
Host-Windows 11, IP Address is 192.168.2.60
VM 1 - ubuntu20 ,apache ...
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Drop ALL the TCP connections (ESTABLISHED,RELATED) in Ubuntu
I'm facing a few hosts sending a flood of requests to my webserver (NGINX). I'm trying to block them via iptables, with ipset and a good old DROP rule.
The rule is effective against NEW connections, ...
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TCP communication to internet broken - no SYN-ACK received
Given following network setup:
Debian bullseye host (Proxmox VE) -> OPNsense firewall doing NAT -> DSL modem (connected via PPPoE) -> Internet
The host isn't able to establish a tcp ...
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Causes of packet loss on multiple persistent tcp connections simultaneously?
The issue was detected while analyzing some application logs, which reported few seconds long spike periods when messages from multiple clients are received on the server with a substantial delay (up ...
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LWIP TCP SERVER Hangs
I'm using LWIP v2.1.3 with TI F28388D Controller. I'm using LWIP as TCP server only mostly in ping-pong mechanism like :
Client
Server
PSH-->
<-- ACK
<-- PSH
ACK-->
A windows client(...
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What does "no ports" on netstat -s mean?
On Windows server 2016, when I execute, in a cmd prompt, "netstat -s" I get a bunch of statistics. One of those is "No Ports".
What does this mean? Is this the number of times ...
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Why are certain TCP connections extremely slow, except while running a packet capture on the router?
I have a weird issue with my MikroTik RouterBOARD hEX - RB750Gr3 (running Router OS 7.8).
Certain TCP connections are extremely slow, for example this 93 KB file takes ages to download from the ...
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What is causing large TCP messages to have low throughput in one direction when using ethernet-to-wifi bridge?
I have two computers, Orin and NUC, which are connected via ethernet cable directly.
NUC is connected to a router with internet via WiFi (for completeness, not relevant to problem, I hope), and is ...
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Can't connect to MariaDB from internal VM Structure
S1
Virtual Machine 1: Ubuntu app server
Virtual Machine 2: MariaDB 1
S2
Virtual Machine 3: Ubuntu app server
Virtual Machine 4: MariaDB 2
from vm04 and 03 I can connect to DB1 with connection string ...
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How to allow a tcp service (not http) on custom port inside kubernetes
I have a container running an OPC-server on port 4840. I am trying to configure my microk8s to allow my OPC-Client to connect to the port 4840. Here are examples of my deployment and service:
(No ...
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OCF resource agent/script for permanently checking tcp socket on layer 4?
How to utilize the OCF, Pacemaker and Corosync to permanently check the availability of a tcp socket?
For the handling of certain services from within Pacemaker/Corosync I would like to constantly ...
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Socket In TIME_WAIT on Client when exit, but not on restart
Linux Server (port 7000)
Windows Client (port 8585)
Scenario 1: Client Restart
Restart on client
Server socket read returns -1, gets errno 104, Connection reset by peer
Server closes its socket ...
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ssh tunnel high latency with multiple connections
hi I'm running an Ubuntu 20.04.5 server I'm using it for dynamic port forwarding kinda like a vpn but the problem is when I'm downloading something or there is multiple connections ping increases ...
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Is there a way to exclude a network interface from being bound via INADDR_ANY?
In network programming, it's common to pass INADDR_ANY (or IN6ADDR_ANY) as part of the second argument to bind(), telling the networking stack that you want the socket to receive connections/traffic ...
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Can no longer connect to server (an error occurred during the pre-login handshake)
Apologies if this isn't the place to ask this, or if it isn't enough information to go off of. I'm pretty new at this and don't know what or where else to ask.
Since two nights ago, nobody can connect ...
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tcp syn is blocked, cant make a connection
so this is my current setup of openvpn+stunnel
user>>internal-server-A(as stunnel client)>>main-out-of-country-server(running openvpn and stunnel as server)
it worked fine in a restricted ...
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Cannot bind to tcp port but no application listens to it
I am looking for a way to find out any process that may prevent binding to a port on a windows 10 machine.
My issue is that I have a server application that cannot open a socket on port 7777, ...
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Trying to proxy tcp traffic through a distant server
During the past few days I tried a few things to make my VPS proxy tcp traffic (depending on port) to my home server (both ubuntu servers).
Client <------> VPS <------> Home server
To be ...
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Which machine is actually closing the TCP socket and why?
I'm working on a C# application, handling TCP sockets.
I have a server application (Hercules) on the remote machine, trying to keep a socket open.
I have my application on my machine, subscribing to ...
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Routing only tcp outgoing traffic through a tun0 interface
I have an ubuntu 20 system, and I'm trying to create a tunnel between my system and a remote server since my client system can't have any incoming/outgoing TCP traffic.
I created a tun0 virtual ...
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How can I avoid the error TCP_MISS_ABORTED/000 when uploading files through squid?
While uploading big files, > 10MB, through a squid V5.6, I noticed that they failed and/or were retried.
The error has been logged multiple times in the logs:
1671092710.452 423 ::1 ...
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Why is there no drop-down option for selecting auto-scaling group when creating a new TCP target group?
And bonus questions while I'm here:
Why does AWS not show which Elastic Network Interface is being used in the Load Balancer details? (at least I couldn't find it)
Why do auto-scaling groups let me ...
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NFSv4 TCP reconnect fails after network failure due to iptables not tracking connection
I have a NFSv4 setup via TCP, /etc/fstab:
nfs-server:/share /mount nfs4 tcp,hard,intr,rw,port=2049 0 0
A few days ago we had a network failure and multiple clients are still stuck trying to ...
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Is checking broken TCP packets still a thing?
I often see samples of IPv4 rules for iptables which are there to stop what is viewed as invalid or broken TCP packets. Certain combinations of TCP flags should never be used.
Here is an example of 4 ...
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How to regulate the random ip and ports fired by SSLH demultiplexer?
I followed this tutorial to install the SSLH package to handle both web hosting and openvpn in my ubuntu 18 server.
However, my server can just handle very limit public incoming port, such as 80,443,...
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Client TCP segments arrive in batches
The scenario is the following: a WebSocket server and clients exchange messages at some pace (like 40-50 times in a second). However, for one client, once in a few minutes I'm observing that there is ...
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Windows 10 and OpenSSH to encrypt a local TCP port
I'm working on a Windows 10 machine. I wrote 2 apps: server and client.
Both of them communicate via standard TCP sockets, no encryption.
I installed OpenSSH, no certificates at the moment, just ...
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redirect outgoing dns queries to localhost using iptables
Problem
There are some outgoing TCP DNS requests in my Ubuntu server that I couldn't control them to be resolved by Unbound on 127.0.0.1:53 which uses 208.67.222.222 to resolve everything, and I see ...
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TCP retransmission inside of docker network
Just lately our server started experiencing increased CPU usage by the php(Symfony) and mysql processes. For quite some time we been trying to find the cause and we found out that we have big amount ...
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Where does Ubuntu log TCP connections?
When doing some network security checks (on which I am an amateur) for my office PC, I discovered a few unknown tcp6 connections (with netstat -nt):
Active Internet connections (w/o servers)
Proto ...
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REST requests to an API falls in timeout randomly
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I developed a web app that communicate with an external API in REST. Most of the time I have no problem, but a few times (1 or 2 times a day) I have my request which is timed out although the ...
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How to cause a network down event on a server?
This may seem weird, but I actually would like to cause a network failure on a project I'm working on. It's a microcontroller that is running tcp/ip and I just want to see what would happen if the ...
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Is my process not accepting TCP connection fast enough?
I have a process P that listens for incoming TCP connections on one port.
I am observing that sometimes clients have to issue several SYN to get a SYN-ACK back and then the processing of their ...
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How does TCP (and other packet-based protocols) avoid conflicting bits?
Scott here.
I was thinking about how packet-based protocols, like TCP, avoid conflicting packets. It must've worked somehow because in the early networking days before switches we had hubs, which are ...
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tcp.analysis.bytes_in_flight times lower than communicated window size
I noticed that when I'm copying a file over SSH (not SFTP) the communicated TCP window size is ~ 250k, but the actual bytes_in_flight never raise above 50k. What could be the reason? Does Windows ...
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What exactly makes TCP limit Cwnd with "cubic" congestion control
I have slower than expected download speed from a server (Debian sever->Windows PC, if that matters). Iperf3 shows no retries but confirms the slow bitrate.
Iperf3 output (iperf3 -s on windows PC, ...
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How AT commands can be used to know the TCP buffer status?
Atmega328p interfaced with ESP8266, vibration sensor. atmega reads vibration data from the sensor at a frequency of 10khz. Each value is sent over UDP using esp8266 UART-Wi-Fi passthrough mode to a ...
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Early warning of port exhaustion in Linux
AFAIK, port exhaustion happens when a host is trying to establish a lot of connections to another server and the sessions used up all the available ephemeral ports. e.g.
192.168.1.1:port -> 10.20....
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Every four hours after reboot TCP connections fail to establish, while ICMP ping is still OK
Every four hours after server reboot TCP connections fail to establish in both directions. The problem lasts several minutes then gone.
No events in syslog seem to be relative, even in dmesg.
ICMP ...
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iperf3: error - unable to connect to server: No buffer space available
I am testing usb to ethernet adapters by using iperf. The product I am testing has 12 ports to test, and I have 12 usb to ethernet adapters each having their default ip address.
I am using Test Stand ...
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Redis cannot bind a specific ip address?
I'm new to redis, but I want to set one up on my Raspberry Pi 4 (RP) for using it in a Django application (with celery).
On my RP I have installed a firewall, ufw, and allowed incomming traffic from ...
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Why is TCP doing RTO based retransmits (200ms+ wait) vs other fast-retransmission mechanisms?
(Trying this forum after the question was deemed off-topic for Stack Overflow & Network Engineering)
I am investigating an issue where we see occasional 200ms+ spikes in a simple tcp client/server ...
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