Questions tagged [tcp]
The Transport Control Protocol (TCP) is a low-level part of the protocol stack used by the Internet. It sits directly above the IP layer and is responsible for making sure that dropped packets are resent.
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Anyone know of a TCP-based tunnel protocol linux will support?
I have a lossy (1%) 10gig link between geographic locations which supports legacy systems that have non-tuneable TCP stacks. They have horrible throughput across the link because their TCP stacks ...
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Question on encrypted DNS over Quic? How is it encrypted?
Suppose,I am using DNS over Quic. Since it is an encrypted protocol as it claims. My question is if intermediate servers cannot see my dns query, how will my dns query be resolved?
It says that the ...
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Established but hidden TCP connection
On computer 10.196.111.161, I can see the following established tcp connection:
[10.196.111.161]# netstat -natp | grep 7000
Proto Recv-Q Send-Q Local Address Foreign Address State ...
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socat et al.: run a command when incoming connection is received
Let's say one is listening on a tcp port for an incoming connection using socat like this:
$ socat file:`tty`,echo=1 "TCP-L:8080"
Is is possible to run a command (just once) when connection ...
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Why does netstat show my socket tutorial program having a port of "x11-1" instead of the port I set in code?
I am trying to learn about socket programming, and I have the following function to set up a socket:
29 int CreatePassiveSock(char *protocol, char *portstr, int qlen) {
30 ...
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conditional flush tcp sockets on linux
whenever I write data to a tcp socket, it waits until its filled with enough data ex: 64k (max packet size) then it sends data to the wire.
this misses the data at the right time for the other end.
...
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How can I redirect traffic for a specific user to connect to another server?
what I intend to do is transfer the traffic of just a specific user to another server (IP). with the commands below it will work very well to transfer only the traffic from the entire server, which ...
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Linux socket modes of IO
There are three modes of i/o. They are Programmed IO, Interrupt IO and DMA.
My understanding is, Programmed IO requires CPU to busy-wait while Interrupt IO by nature, is ansynchronous.
Where can I ...
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TCP Congestion Window in Linux
I'm making some test between two peer (CentOS7) in a 10Gbit network with iperf.
The configuration in /proc/sys/net/ipv4 and /proc/sys/net/core are exactly the same, so every socket buffer default size ...
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How to clean TCP Established state sockets?
I'm experiencing an issue with my rented VDS server, which is running Ubuntu 22.04. To secure my server, I have enabled ufw (Uncomplicated Firewall) and allowed access only to two TCP ports: 2222 for ...
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Linux corrupts customized TCP option
I am facing a peculiar problem with TCP options in k8s/Cilium/Kind.
I have added a customized TCP option to the SYN packets being sent out from an endpoint using Cilium's bpf_lxc program (an eBPF ...
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Problem with connection between custom application and qpidd compiled on ArchLinux while running them on Debian
I have a custom application and qpidd (Qpid version 1.36) which had been built on ArchLinux. Default TCP with default settings is used as protocol to connect to the running qpidd, and the connection ...
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Problem using Iptables for filtering traffic on a network interface which is a bridge port, on a specific tcp port
I am using iptables as firewall to filter traffic. I want to block traffic on a network interface on a certain tcp port (I'm testing on port 22). The network interface is a bridge port, so I'm using ...
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TCP connect() call to device on local network very slow
I am running a local DHCP server using isc-dhcp-server on Debian linux, address 10.0.0.1.
I have a relay on 10.0.0.99, to which a pulse is sent every 4 seconds or so via an HTTP request.
The pseudo-...
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TCP/IP client-server slow communication
I made some network application.
It is a client-server solution using the TCP/IP protocol.
Clients connect to the server.
They make several connections every second.
Communication consists of units of ...
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prometheus node exporter sockstat
I'm looking for the meaning of the node_sockstat_TCP_mem_* metrics.
The output of the node exporter describes them as follows:
# HELP node_sockstat_TCP_mem Number of TCP sockets in state mem.
# TYPE ...
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How does sshuttle actually forward TCP packets? How is it different from a full-fledged VPN?
Here is the scenario:
On myHost (1.1.1.1) I run:
sshuttle -r user@remoteHost 0/0
Now, if I check the my current IP on myHost with an http request directed to one of those services that echo your IP, ...
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No incoming TCP/ICMP packets with Huawei Brovi E3372-325 LTE USB Stick
I'm connecting a linux machine using a nowadays popular Huawei Brovi E3372-325 LTE USB Stick to the internet (more precisely, to a private APN, where IPv4 is used). The special requirement is that ...
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TCP port visible from inside nor outside
I've used autossh (reverse) connecting to my server. The ssh side works like used to. But in an ARM64 system, my Ubuntu has less possibilities but this is another story (...).
So what I see whit nmap ...
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Unable to send more than 60 bytes TCP packets using traceroute or tcptraceroute
[root@host33cn ~]# traceroute -M tcp -f 255 -m 255 -q 10 -w 1 -p 9101 10.11.1.6 1400
traceroute to 10.11.1.6 (10.11.1.6), 255 hops max, 60 byte packets
255 host05cn.zen.com (10.11.1.6) 0.112 ms 0....
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GNOME Shell in CLOSE_WAIT state
I noticed that the gnome-shell has been sitting in the CLOSE_WAIT for quite some time now. It shows it was connected to 8.43.85.4:443 and when doing a reverse lookup, I see the IP maps to master2....
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How to build kernel after modifying specific files?
I'm new in kernel development and I modified two kernel files for a research project. Now, I already know how to do a fresh building of the kernel source code and that is what I did. I'm asking if I ...
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NFS client (ubuntu) froze after a while with openbsd server / FIN_WAIT_2
I have an openbsd server sharing directories through NFS protocol. After I installed a new version of ubuntu on the client, I still mount NFS directories however after a (random) time: nautilus, ls ...
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why is proxied TCP traffic much faster than routed/VPNed TCP traffic
I have a VPS which can download a file from Server X at 2gbps.
I have a home internet connection which can download a file from the VPS at 1gbps, but from Server X at only 100mbps.
If I use a SOCKS ...
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Applying patch file to ubuntu server
Can someone please explain how to apply a patch file to ubuntu server kernel? I'm trying to apply this patch file which enables the tcp_collapse_max_bytes option in the TCP communication options on an ...
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Unable to read data from gpsfake
I saved the following NMEA-messages to the file messages.txt:
$GPRMC,131131.00,A,5956.4298,N,03015.4464,E,00.00,310.5,130123,,,D*53
$GPRMC,131132.00,A,5956.4298,N,03015.4464,E,00.01,097.3,130123,,,D*...
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How to read TCP congestion control parameters on Linux?
How do I read TCPs congestion control parameters on Linux in realtime for a connection? Specifically, I'm interested in the cwnd (congestion control window) and ssthresh (slow start treshold) in ...
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Linux appears to be connecting to a TCP server that should not exist, for even-numbered ports in the range 32768-60998
I'm attempting to determine why the following C++ code connects to a server that does not exist.
#include <boost/asio.hpp>
#include <iostream>
int main(int argc, char* argv[])
{
boost::...
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command that shows all online connections?
I used TCPView to see all TCP and UDP endpoints in Windows. Is there any linux command/gui that has similar functionality?
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What type of queue is TCP accept queue in Linux -- FIFO/LIFO/other?
I am wondering if TCP accept queue in Linux is a FIFO or LIFO, or any other type of queue?
Asking the same from another perspective: does accept() yield connections in the same order as they arrived ...
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What's the default KeepAlive value for a TCP socket in a UNIX-like Docker container?
I am creating a TCP socket as follows:
_socket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream,
ProtocolType.Tcp);
if (Environment.OSVersion....
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TCP communication between client and server after server IP has been deleted
I created a tcp server listening at [IP1:PORT1] and connect to it via a client using [IP2]. On both the client and server, SO_KEEPALIVE and TCP_USER_TIMEOUT are enabled with below config values.
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cyrus imap does not start lmtp tcp socket, error message: Servname not supported for ai_socktype, disabling lmtp
Problem:
When starting cyrus imap with the following line in /etc/cyrus.conf:
SERVICES {
...
lmtp cmd="lmtpd -a" listen="[192.168.50.100]:lmtp" prefork=1 proto=tcp4
}
...
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source&dest ports over port forwarding
I'm implementing a firewall module, and I have the following system:
A "client" with ip 10.1.1.1
A firewall
A "server with ip 10.1.2.2
The networking in this system is implemented ...
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Linux SO_RCVLOWAT being violated by epoll according to FIONREAD
The more traditional way of dealing with sockets is to have a buffer per connection, and to incrementally read as many bytes as possible once the socket becomes readable.
With a framed protocol ...
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Understanding netstat: are these TCP connections actually direct ones?
I am reading about networks, and in an example output table from netstat -n (from visiting a hypothetical website hosted from 216.40.231.195), my book shows a row that looks like this:
Proto Local ...
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Disable port 8910 and then again enable when required in my linux based server
As you see below jsvc.exe is running on 8910 with PID 23943.
[root@abc-163 ~]# netstat -tulpn | grep :8910
tcp6 0 0 :::8910 :::* LISTEN 23943/jsvc....
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SSH connection and TCP packets
I have an ssh server at IP YY.YY.YY.YY listening on port 5022 which shows the following traffic (with TCPDUMP) where XX.XX.XX.XX is an external UNKNOWN IP,
10:34:58.879055 XX.XX.XX.XX.59800 > YY....
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forward remote tcp port to local port
I have the following setup:
The unit constantly tries to connect to the Remote Server on a specific known port.
On the Remote Server, there is nothing but open TCP ports.
I want to forward the Remote ...
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CLOSE_WAIT not visible on the kubernetes node
Debugging a tcp: out of memory error, I found that a process (from a container) has a lot of connection on CLOSE_WAIT status aka 08 when I cat /proc/XXX/net/tcp
But neither netstat or ss were showing ...
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How to see process ID of TCP?
When I want to see the process ID for an application I do ps -aux | grep <application>. For example, when I do ps -aux | grep ssh I see the process ID for SSH.
But when I do ps -aux | grep tcp ...
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Number of open sockets in /proc/pid/fd does not agree with netstat
I'm running into a weird socket issue when running my own crawler. It opens and cloees a lot of TCP sockets rapidly due to the protocol design. It's something I have to live with. I'm very sure in ...
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Is it possible to detect if a process is trying to create a socket connection but the remote server refused
Let's say that I have a process on my local Ubuntu. I want to know if it would use some socket connection(TCP or UDP) to connect some remote server, which has been turned off, meaning that any ...
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Debian Router (DIY) Website Timeout Problems
I've been setting up a DIY router using Debian. I'm at a point where it's routing traffic to the internet for my client devices. However I'm having trouble accessing websites.
Some websites load ...
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How does a telegram bot work in Linux?
I wrote a simple telegram bot and it works great without conflicting with my firewall. But my question is this, in the firewall I have ports 80 and 443 allowed for my site, but when I write a TCP ...
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TCP packet excess delay
I am sending packets of known length from client (63396) to server (50001)
frameTime 1659456858651175 frameSeq: 0 Packets 1 bytes 23425
frameTime 1659456858667639 frameSeq: 1 Packets 1 bytes 19556
...
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How to "properly" read remote sshd server version with bash
I'm trying to read remote SSHD server version with bash without installing an extra tool :
$ cat < /dev/tcp/x.y.z.t/22
SSH-2.0-OpenSSH_7.2 FreeBSD-20160310
^C
CTRL+C is needed, so I tried to read ...
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Check what service is running on a specific tcp/udp port
I'm looking for a command-line utility that allows me to check what service (eg: http/ftp/ssh) is running on a specific port of a remote machine.
An example of how I imagine a program like this would ...
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OpenVPN TCP: connect to [AF_INET]10.0.2.15:110 failed: Connection refused
I have two virtual machines with which I am trying to establish OpenVPN connection (debian1 as server, debian2 as client), but keep getting the error mentioned in the title. I need specifically tcp on ...
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How to debug Linux TCP slows/packet loss
I'm trying to track down some particular network paths which are slowing down to about 200KByte/sec. I see this performance through various tests including with scp, rsync and iperf3:
$ iperf3 -c 157....
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