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.

learn more… | top users | synonyms

2
votes
2answers
53 views

Binding two incoming TCP connections

I have a client to connect multiple devices. For not paying monthly static IP fee per device. We plan to change the architecture. In this new architecture devices connect to a server. Instead of ...
4
votes
1answer
572 views

How to investigate a random reset on TCP client port connected via loopback interface to a server

I have a test suite which initializes a server on the localhost and then runs thousands of stress tests which include starting and stopping clients connecting to this local server on same machine. I ...
3
votes
1answer
104 views

Why are these connections not classified as “established” under conntrack?

I have the following rule for iptables: -A OUTPUT -m conntrack --ctstate ESTABLISHED -j ACCEPT such that outgoing connections not classified as established will be logged. Occasionally, the ...
3
votes
1answer
99 views

Force application to use specific port on Fedora machine

I have an application on my fedora machine that sends SIP TCP requests to the server. The application chooses a random source port to send the requests. Is there some way I can force the application ...
3
votes
1answer
130 views

detect process that executes portscans

I have to administer an ubuntu 12.04 server, where there seem to go portscans to the whole subnet. How can I find out the process that does the scans? pstree init─┬─acpid ...
2
votes
1answer
42 views

socat duplicate stdin to each connected client

ncat (from the nmap folk) has a neat default action of duplicating any input to all connected clients. E.g.: Start a server on terminal 1: % mkfifo messages % exec 8<>messages # hold the fifo ...
2
votes
1answer
67 views

Capturing data from a Fluke 1620a via Bash /dev/tcp file descriptor

I am currently trying to develop a script that will connect to a Fluke DewK 1620a Themo-Hygrometer and pull the current temperature and humidity readings from the device. While these devices have a ...
2
votes
1answer
98 views

bound, but not listening process

python code for simple daemon import socket import time import signal s=socket.socket() s.bind(('127.0.1.1', 20201)) def stop(*a, **k): global work work = False ...
1
vote
1answer
98 views

Relay server for generic TCP traffic?

Here's my situation: I have a computer (Mac) on a school network that I want to port forward TCP 5222 to for ejabberd, but of course I can't. I have a server at home (Mac with FreeBSD VM) that I can ...
1
vote
1answer
408 views

How to limit all tcp traffic to the network interface the session was initiated on?

I have an embedded linux system with two network interfaces (lan0, wlan0) that are configured to the same subnet. A server on this system accepts tcp connections on both interfaces. How I can assure ...
0
votes
1answer
34 views

Linux drop packets if received from another equipment

Problem description : When I establish a VPN connexion between a VPN client and my home server, if the connexion are both across my firewall (pfSense) or are established directly, the connexion is ...
0
votes
1answer
17 views

What happens to TCP when a write fails to enqueue with the device tx ring?

Lets say the device tx ring is full and you do a normal C non blocking write(fd, buff) to enqueue data in the TCP SND buffer. What happens when this fails? In UDP - the packet would be dropped but ...
0
votes
1answer
216 views

Which port to open for Google HangOut Video Conference

We need to open the necessary ports for Google Hangout VIDEO Conferencing in our firewall. Unfortunately my netmon trace shows Port 51355 and 51336 to be active; which is not at all what the Google ...
0
votes
1answer
17 views

tcpdump Filter with certain file types?

I use the unix command tcpdump with these extensions -A -s0 -ien0 port 80 I know how to add, for example a new host, that would be and \ host random.com Can I sniff for certain filetypes? I have ...
0
votes
1answer
117 views

What are the other congestion control algorithms specially designed for lossy Wireless Networks like LTE and WiMax?

I am trying different congestion control algorithms for getting maximum throughput and minimum delay across my setup for TCP flow.Please suggest other available algorithms apart from Veno, ...
3
votes
0answers
38 views

TCP Westwood implementation available?

Is there a way to install TCP Westwood congestion control algorithm module for FreeBSD? If not, maybe there's a source code available that could be compiled into a loadable Kernel module? Thank you ...
3
votes
0answers
406 views

graph TCP connection performance based on `ss -i`

A nearby question has brought to my attention the ss utility on Linux, another utility to investigate sockets. It would appear that it may be a great tool to monitor the performance of, say, an ssh ...
2
votes
0answers
76 views

TCP, UDP, etc. works, HTTP(S) does not

I have been trying to set up Debian Jessie on an old Dell Inspiron 300m. Right now the problem I have is, the ethernet connection only works partially. ICMP works. I can ping IPs and FQDNs. UDP ...
2
votes
0answers
79 views

How do I find out how long a socket is in CLOSE_WAIT?

I have a server relatively with a high number of sockets in CLOSE_WAIT I want to know the age of each socket, to know if it's a real problem (sockets not getting closed) or that the sockets are ...
2
votes
0answers
69 views

Exclude a loopback interface or address from processes listening on the “any” address

I'm trying to create a setup where I can connect to some service running on a host only reachable through a SOCKS proxy by the host's actual name and the port the service actually uses (so that ...
2
votes
0answers
82 views

Why isn't hydra being disconnected?

I have SSHD running on port 5800 on some machine. (It is a my machine at home.) If I run this manually in a terminal: # ssh someIP -p 5800 The connection is lost because I am disconnected after 3 ...
1
vote
0answers
32 views

What does an inode for a socket contain?

I read somewhere that the inode for a TCP socket would contain the buffer space. Is that true, and if so, does it mean that the inode contains a memory address for the buffer space used by the ...
1
vote
0answers
111 views

telnet connection closes

I am running hdfs in one machine. I am trying to write into hdfs from my second machine. I got connection refused error and got this link in the error itself: ...
1
vote
0answers
41 views

How can I log outgoing TCP traffic including the full path of URLs?

I use a program regularly on Linux that makes a TCP request when it starts up and updates a file with an access token before launching. I'd like to write a batch script that makes this request (using ...
1
vote
0answers
155 views

Rsync - Corrupted MAC on input

Background I have a script on my NAS which is a Synology DS212J which is running on a special distro where uname -a gives me Linux DS212J 2.6.32.12 #4493 Wed Jul 16 11:37:16 CST 2014 armv5tel ...
1
vote
0answers
287 views

tcpdump not capturing http or tcp/ssl traffic

I have been trying to learn tcpdump and I am using this command to attempt to monitor my network: sudo tcpdump -I -i en1 But this gives me a bunch of stuff I don't want, so I used this version to ...
1
vote
0answers
428 views

Improving TCP performance over a gigabit network

I have two machines both network cards speed is 10Gbps. The inbound bandwidth between the two machines is 10Gbps, the outbound bandwidth internet bandwidth is 500Mpbs. Both machines are using public ...
1
vote
0answers
148 views

Command for finding open ports

On my linux servers I have this alias set: alias ns="sudo lsof -Pi|grep -v ESTABL|grep -v CLOSED|grep -v -e '->' | tr -s ' ' '\t' | awk '{print $3 "\t" $8 "\t" $5 "\t" $9 "\t" $1}'| column ...
1
vote
0answers
447 views

How to redirect/forward between a tun/tap device and a socket using linux tools?

I have a socks5 proxy that is bind to eth0. It opens two ports, Port1 is used to connect to remote (for example a http server), Port2 is to listen for clients to connect. Then I created a tun device. ...
1
vote
0answers
69 views

configure allowed_tcp_congestion_control via config files in linux kernel

I am trying to come up with a custom set of TCP congestion control variants as part of the tcp_allowed_congestion_control. I do have multiple variants on my tcp_available_congestion_control list but ...
1
vote
0answers
59 views

Can we Bring Up eth1 after removing e1000e modules?

I am trying to setup TCP in RTnet. I am not sure whether its possible. I read that RTnet is not supporting TCP. Is that so? So now I am trying to setup rteth0 as server and eth1 as client. To setup ...
0
votes
0answers
25 views

How to enable Tcp\Ip remote connections in Centos 7.0

I am running Centos 7.0 using VMPlayer . I have set a private network shared with the host (Windows 7) . On my Centos Server i have opened a tcp listener on port 10102 . I could not connect to this ...
0
votes
0answers
19 views

How much of Linux's recent TCP bufferbloat remediation also applies to SCTP?

I am looking at rebuilding an existing communications sub-system within a shared-nothing cluster. The current message protocol is built on UDP but layers on reliable, in-order delivery and ...
0
votes
0answers
33 views

Linux, dev/tcp validation and kill the process with timeout

I have this part of code, I need to validate if the connection was ok or not, AND, if the process is running more than 3 seconds, it will be killed. But, I dont know how to keep the value of the ...
0
votes
0answers
76 views

Opening a TCP port in Linux

I am trying to establish a TCP socket between my linux server and my client running on my laptop. The TCP server code I am running is, from socket import * HOST = '' PORT = 1999 ...
0
votes
0answers
25 views

why do I have so many open socket handlers and netstat DGRAM entries?

I run on a RPi (Raspbian 3.12.35+ #730 PREEMPT Fri Dec 19 18:31:24 GMT 2014 armv6l GNU/Linux) a daemon in Python 2.7.8 which queries various APIs via requests and provides itself an API for another ...
0
votes
0answers
44 views

cannot change tcp-segmentation-offload

I have been doing tests with tcp-segmentation-offload on and off, but now I cannot seem to change the parameter anymore, it is stuck on "off" (I can change generic-segmentation-offload) ...
0
votes
0answers
61 views

How to check number of connections

My server have high loads. CPU usage is low. Memory usage is low. IO is low. So I improve maximum number of connections in cpanel. Things are working. However, where can I see detail? How do I ...
0
votes
0answers
39 views

How can I reduce the TCP connection time for web resource requests at the OS level?

I'm experiencing an issue where almost every request for a resource on a web application has a 100ms - 500ms delay in the "connecting" phase as reported by firebug, which is the time it takes to ...
0
votes
0answers
102 views

different ways how Linux TCP/IP stack terminates connection

I have a Linux machine which connects to SSH server with SSH client(OpenSSH_4.1p1). SSH client machine has IP address 10.10.11.1 and SSH server has IP address 10.10.10.1. SSH client has kernel version ...
0
votes
0answers
169 views

Socat execute commands on remote

I am playing around with socat and wanted to execute commands to hosts that connect to my IP PORT running socat. In this case I am trying to dump a file on localhost and this is how I am trying to ...
0
votes
0answers
49 views

Can spawn-fcgi be user for tcp/udp server

Spawn-fcgi by lighty labs It only uses unix socket functions socket(), bind(), connect(), listen(). Is it possible to use it not for FastCGI server, but TCP or UDP server?
0
votes
0answers
88 views

Is it possible to move established connections on one port, to another without dropping data?

this problem has been bugging me for a couple of days now. I can't figure out a good enough solution using iptables without having dropped packets. So here is the back story. Say I have a client ...
0
votes
0answers
153 views

How to make Network alive but speed low, slow for upload, download?

I have own application written (Python, Java) which does upload/download for streaming. Now in my local office network and home network setup i can't simulate slow/low latency network (as a result i ...
0
votes
0answers
227 views

No ports can be found using port scan

Problem: I have a laptop and a server (Home-Server) with fc17. They are both using the desktop environment. I am trying to set up a VNC server on Home-Server so that I can set everything up without ...