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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TCP connection severing in Two arm load balanced environment using Kemp LoadMaster connecting to Centos servers
The configuration is one that I inherited but the connection from the LoadMaster to two appserver ends up occasionally getting severed. This will happen to each server independently, and only seems ...
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Automatic TCP SYN - cookie activation
I am simulating a SYN flood attack on a Raspberry Pi 1 with KALI Linux (ARM) installed.
A similar message as mentioned in this post was printed after performing the attack: How to avoid syn cookies.
...
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TCP session refused immediately after accepting it
Host_A tries to send some data to Host_B over TCP. Host_B is listening on port 4712. Host_A is a remote PC connected on a dedicated WAN. Host_B is a local embedded device based on embOS OS, connected ...
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Setting Up WAN + LAN Network with pfSense in VirtualBox - Troubleshooting TCP Connection Issue
Hello,
I am currently in the process of configuring a WAN + LAN network within VirtualBox using pfSense (VM) as the router in my LAN. The primary objective is to establish communication between a TCP ...
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First attempt at connecting to any TCP service fails
Symptom: The first attempt at connecting to a TCP service (https, ftp, or ssh) fails. The second attempt succeeds Subsequent connections will work until there is a 15 minute period of inactivity, in ...
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All tcp ports are not reachable on localhost (MacOS 13.4)
A friend of mine asked for help, basically any app listening on some local tcp port on localhost can't be reached. For example a node.js server running on port 8080 or 3000.
Executing the command sudo ...
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Proxy TCP connection to different hosts depending on the origin host
I have a home server exposed with NoIP, with a wildcard domain.
I have some services that run on some TCP ports (mainly game servers), and I am trying to sort of "assign" each of them a ...
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OpenVPN TCP connection to firewall failing: unknown error
I am encountering an error when attempting to connect to my office using OpenVPN. The error message:
Tue Jul 18 12:34:52 2023 WARNING: Compression for receiving enabled. Compression has been used in ...
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IP Based Rate Limiting for a TCP passthrough vip
Trying to set this up for one of the applications. We use Nginx under the hood. Is it possible to set up an IP-based rate limiting for a TCP passthrough VIP?
I understand that it is possible to set ...
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php sqlsrv error TCP Provider: Error code 0x271D
when i run php script from browser sqlsrv mssql connection working.
but when i execute php script via ssh
command "/opt/alt/php-fpm70/usr/bin/php path/to/script.php"
sqlsrv_connect give this ...
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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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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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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 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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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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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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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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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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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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Continuous RST, ACK flags from the same source
Can anyone help me better understand what is going on here? I keep receiving "broken pipe" errors that say the connection is being reset by the peer. Also, I thought 192.168.114.30 was the ...
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How does linux / netfilter / iptables "know" if a packet is meant for itself for to be forwarded
I have setup an ubuntu box as a router manually , using iptables + NAT.
But I was wondering, how does the "middle-router" know if the packet is meant for it or to be forwarded?
I tested this ...
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156
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TCP packets being lost
I have some TCP packets being lost. I have monitored the interface with tcpdump pcap file - https://www.dropbox.com/s/7m3hr1b7065tenx/tcp.pcap?dl=0
I noticed that when I lose packets I only get 5 ...
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How can I inspect everything that happens before a TCP handshake
On my local machine when I connect to a remote linux machine with netcat I can only see 3 related packets(the tcp handshake) in Wireshark.
I'm pretty sure there's more that happens before that(router -...
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proxy a Ssh server that is on my home over a vps
I want to proxy my home SSH-server over a VPS from Dedipath, but I don't know how it works. because I already tried it with many tcp proxies and they didn't work.
My VPS has Debian 10 and my home ...
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Debugging why the packets get dropped
I've started on stackoverflow, then after some investigation asked on superuser, because it looks like network or kernel (mis)configuration, but probably I need some seasoned network engineer to help:)...
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Difference between TCP Segment Data and Data on a Wireshark capture
I am trying to replicate some TCP communication that is sent from MongoDB and I have been able to replicate it byte by byte and it is still not being recognized.
The only difference I could find when ...
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685
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Server 2019: slow upload
I have both Windows 10 Pro and Server 2019 VMs set up on the same host.
From the Server 2019 instance, using iperf and the same NIC/driver as the Windows 10 guest, I get ~3Mbps on a theoretically ...
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Why we get TCP retransmissions through IPSec Site-by-Site Tunnel
We use two pfsense firewalls at two locations and have connected the locations using IPsec site-by-site. That had worked well for a long time, now we had installed the 2.6.0 update at both locations ...
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TCP communication on port not responding on different Availability Zone or Subnet
I'm a little curious and confused about this situation. We setup a monitoring instance scraping an exposed endpoint on 2 different instances. Both on same VPC, same security group, same route table ...
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135
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UFW route not responding
Hi i tried to make a server where every software running on it is in a vm.
i tried using ufw to route the requests and it worked ... locally.
when i tried to connect to one of my vm using a vpn i saw ...
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The packet goes through the other router
I want to connect two hosts in parallel with two different models of virtual routers.
These are made redundant by VRRP.
Originally, packets are sent through only one of the routers.
However, when the ...
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Bytes-in-flight higher than receiver window in frozen client connections
I am dealing with sort of a "ghost issue". We have an endpoint URL that some people can use at all times with no issues but others have a frozen connection on the client side (checked with ...
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How to find the symmetric key algorithm being used for a TLS connection in Wireshark?
I'm doing a TLS Wireshark lab and I can't find any information in Wireshark, the lab, or online how to find this answer:
What symmetric key cryptography algorithm is being used by the client and ...
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153
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How to get syn flags, ack flags, sequence number and acknowledgement number in tcp packets with nfqueue?
I am working on a project which can redirect the network traffic in tcp (packets sent by client to server1 will be redirected to server2) with netfilterqueue, so I need to classify the packets by ...
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Traceroute - Header Link CURL result Issue
We have systematic CURLs run every 15 mins - 2 hours from this system and logging their status. Every other CURL for the past 2 months has succeeded except this. Is there a way to identify why this ...
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698
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High cpu usage over TCP
I'm running haproxy 2.4 and when the haproxy is configured in tcp mode i get a high cpu usage.
Example:
Running the stress tool to generated arround 30k connections:
./pst -c 100000 -r 100000 -u ...
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242
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AWS ALB Handshake resumption
I have a problem where the AWS ALB TCP is initiated and every request which causes unnecessary latency of 0-150ms
Example from postman to show what happens at every request. DNS lookup, TCP Handshake ...
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558
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rsyslog - Lower throughput when using omfwd with TCP vs UDP
TLDR;
I'm getting significantly lower throughput when forwarding syslog messages with rsyslog on a Redhat server with 32 cores and 128Gi RAM to a remote server using TCP instead of UDP syslog in the ...
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908
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Clamav is very slow with tcp
I'm using clamonacc on my desktop computer and servers. I use a raspberry pi as clamd server. The clamd process only uses ~25% of all 4 cores so with htop I see it's using like ~100% and 400% is the ...
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syslog-ng / telegraf : EOF occurred when idle - incompatible?
This is a follow-on question from this previous question, created because I found out more information and it's cleaner to pose this as a new question.
I'm using syslog-ng OSE v3.31.2 to receive ...
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netcat no reaction to syn packet crafted with gopacket
I want to do some experiments with TCP packets. Therefore I am using the gopacket (v1.1.19) to craft packets and send them onto an interface.
I have this code for creating a SYN packet and putting it ...
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So many TCP packets to domain server from domain clients
I have Windows Server 2012 R2 which controls my LAN. Everything was working fine (Shared Folders, Folder Redirection and so on) for a two months. But suddenly, there occured delay on communication ...
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Strange TCP sequence from a device
I'm debugging strange connection reset problem in Java and got the next
Wireshark capture:
What can be the cause of repeating that ACK? I'm sure that the device received data correctly as it is ...
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318
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How to make bind force clients to connect via TCP only?
I want to set up an experimental nameserver that asks clients to send requests via TCP only by sending back packets with the TC bit set. For that purpose I tried to work with the rate-limit parameter ...
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How to toubleshoot port blocking issue
I'm forwarding port 80 of a web server to the public interface of the firewall, which is then mapped to a domain name so that the server can be accessible from that domain name.
I did this process too ...
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Allowing IP & Port specific traffic for card terminal
I hope you can help me :)
I am setting up a credit card terminal in my store network. (It‘s just a mobile LTE Router with a static IP address and a switch)
The payment processing provider requires me ...
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TCP connections retains even sessions terminates
We have client/server application running in our environment, we are experiencing an issue that single client having multiple connections to the server, although, there is only one instance is running ...
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Do ephemeral port numbers run in sequence for the whole system, per process or per listening port?
We have an application and we use the ephemeral port number to identify the connection. We listen on two different ports, one for normal connections and one for SSL connections. I want to avoid the ...