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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How do I configure Docker containers to have unique IP addresses that are not the default ones?

How do I configure Docker containers to have unique IP addresses that are not the default ones? The Docker containers will run Apache or some web service. These Docker containers will share one host ...
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How do I get Consul to work so I can get Docker Overlay to work?

I am running CentOS 7 with Docker. I am trying to install Consul on the Docker server. Consul is unzipped. The binary file works for showing the version. I ran this: echo $CONSUL_RPC_ADDR This ...
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1answer
21 views

netcat daemon for calling functions in sh script

I'm new to shell programming and I have created a script that opens a connection to a server of mine. I want to have this script listen for an input from a client node and use that to run a function. ...
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What does TCPRcvCoalesce, TCPAutoCorking and TCPHystartTrainCwnd in netstat mean?

We have some RHEL7 Apache reverse proxies that experienced a performance degradation event. After a few hours, restarting Apache restored performance to normal levels. We are trying to determine the ...
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36 views

Why would all our CLOSE_WAIT connections have 24 bytes in the receive queue?

We have an Apache reverse proxy that is having connectivity issues with the back-end. This results in timeout errors such as this: [Thu Apr 21 12:12:26.031207 2016] [proxy_http:error] [pid 64620:tid ...
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1answer
30 views

log script output to file and terminal at the same time

I have a simple tcpnotification receiver script that logs notifications. At first I just printed the notifications in terminal but then changed script so that notifications are logged in a file. But ...
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1answer
18 views

Connecting to server on localhost with same source and destination port

Here is simple server listening to port 80 of localhost: nc -4 --listen 127.0.0.1 80 Here is the client to connect to server on localhost using source port same as destination port of server: nc -4 ...
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2answers
13 views

Add TCP congestion control variant to Linux Ubuntu

I want to test different variants of TCP in Linux Ubuntu. I have Ubuntu 14.04 LTS with Kernel version 3.14. When I check the available congestion control algorithm using the following command sysctl ...
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27 views

why does nmap shows same ports sometimes as filtered and sometimes as closed?

When I'm scanning port range 4050-4060 of an smart metering device all ports are reported as closed: root@abc:~/rvm/dlms# nmap -p 4050-4060 192.168.1.242 Starting Nmap 6.47 ( http://nmap.org ) at ...
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1answer
47 views

Bash reading from /dev/tcp, without external binaries

I'm trying to read files with bash tcp socket, So on one host I do, nc -l 8888 < /etc/passwd And on another machine, echo </dev/tcp/127.0.0.1/8888 But it didn't read the file as expected, ...
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14 views

Several TCP Window Scale values depending on interface?

Is it possible that TCP Window Scale value set by default on a socket (not raw) depends on the interface used? Where are these values stored?
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61 views

TCP SYN,ACK Retransmissions

The following network trace was recorded on a Raspberry PI running Debian Linux. It seems the Raspberry is not seeing the data packet #36995 for some reason; it is just stupidly repeating his SYN,ACK ...
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1answer
53 views

How to pass received data from netcat to another script as argument?

I have simple bash nc script: #!/bin/bash nc -k -l 127.0.0.1 4444 > filename.out which listens 4444 port for TCP connection. Instead of redirecting received data to filename.out I would like, if ...
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2answers
31 views

Count Bytes by Ports

Using RHEL/CentOS 6.7 -- I want to be be able to know byte counts on IPv4 ports. We have thousands.. I would think counting via IP Tables for that would be a bit unweldy and slow the firewall a wee ...
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1answer
30 views

reading the output of netstat for tcp

If I ssh root@server -R 5901:localhost:5900 and netstat -an I get: Active Internet connections (servers and established) │ Proto Recv-Q Send-Q Local Address ...
2
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1answer
96 views

socat/netcat UDP to TCP

I am trying to bridge a connection between UDP and TCP. The UDP - must listen on port. The TCP - must connect to a server. The purpose of the connection is to control VLC player. I tried netcat and ...
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55 views

Apache Load Balancer Timeout

We have two httpd servers running on RHEL 6 behind a hardware load balancer We are getting timeout errors in our httpd error log. [Fri Feb 19 15:06:49.823372 2016] [proxy_http:error] [pid 15760] ...
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1answer
63 views

Lots of TIME_WAIT in netstat on apache server

What would be the reason for many TIME_WAIT here? Even we have very few ESTABLISHED, SYN connection. [root@www ~]# netstat -natp | grep "210.XX.XX.XX:80" | awk '{print $6}' | sort | uniq -c 1 ...
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1answer
47 views

ubuntu IPTables

I started hosting my game-server on Ubuntu Linux 14.04 I am having an issues ، some enemies/bug abusers log in 2+ characters in the same second then they spam a certain spell/word that lags/stops my ...
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37 views

Netid in ss output is confusing

I'm on an Ubuntu 14.04 x64 machine. I have something running on port 51236 and I want to know whether it's TCP or UDP. So I ran ss -an | grep 51236 and got the following output. tcp ESTAB ...
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121 views

Half-close netcat connection

How can I have a netcat connection terminate the sending half of a TCP connection if its input reaches EOF? I have a (non-standard) TCP service which reads all its input (i.e. until the client sends ...
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0answers
51 views

nginx server never resolves

I have set up an nginx server which is a proxy for port 80 to http://127.0.0.1:3000, but the request never gets through. It just infinitely loads. I have tried sudo /sbin/iptables -I INPUT -p tcp -m ...
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34 views

Cannot access server outside of server`

I have a node server listening on port 80. If I send a request to it like this: request('http://127.0.0.1:80',function(err,res,data) {console.log(data)}) It works. It returns what I would expect. ...
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18 views

Changing the Retransmisson Timeout (RTO) estimation in Fedora

Retransmission Timeout(RTO) in a TCP plays a vital role in the internet. There are many algorithms proposed for calculating the Retransmission timeout. RFC 6298 is used for the estimation of RTO. I ...
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8 views

Claiming node on swiftstack times out

I am trying to connect a node that I have installed CentOS on using SwiftStack. To make this connection, both port 443/TCP and 1194/UDP will need to allow outgoing traffic on your firewall. I have ...
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33 views

WARNING: at net/ipv4/tcp.c:1654 tcp_recvmsg

Our Linux based device (3.7.2) experiencing following issue when we try to do FTP or SCP over WiFi Connection. Same will work on Ethernet Connection or on TFTP. Here is the dmesg log for this issue: ...
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2answers
145 views

How to know if port 25 is blocked?

I am running Debian Jessie 8.1. The VPS provider says that port 25 is open. However, when I installed Rainloop and am not able to use it with the System users. Under the RainLoop admin panel I went ...
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1answer
204 views

Can nmap display only hosts with specific ports open?

Can nmap list all hosts on the local network that have both SSH and HTTP open? To do so, I can run something like: nmap 192.168.1.1-254 -p22,80 --open However, this lists hosts that have ANY of ...
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2answers
45 views

Unable to connect remotely to custom application

I've built an application that listens on the localhost address and a specific port, lets say port 11001. Its on a remote machine with CentOS. I currently have a python script on my local machine that ...
0
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1answer
87 views

pfsense tcp connection between openvpn and lan is broken

I am trying to connect openvpn clients into an internal lan, so they can access a http server. pfSense as well as my http server are running on a virtual machine of my home proxmox node. Both are ...
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20 views

is it possible to read a process's incoming TCP RecvQ?

I have a process running which has a number of incoming TCP connections, all of which show a non-zero RecvQ bit for some reason the process has not gone to read the incoming data. netstat -nap ...
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1answer
89 views

Netstat Listen Queues

What information can I gather from netstat listen queues? Looking at the man page I can see that using "-L" in netstat it shows me the size of listen queues. It tells me information about each ...
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19 views

Can't get websocket- answer from client browser in gawk

I want to make websocket server with gawk. I can pass handshake and send many messages to client, but when i'm trying to listen host to get client's dataframe gawk stops and cant do it. What i'm doing ...
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0answers
12 views

how to remove Queue in send_Q-part of netstat?

I have a tcp-server or may be it is lazy tcp-server because sometime the program dose not take the data from socket and i see some number is send_Q/recv_Q column of 'netstat -tn' command. is there a ...
1
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1answer
91 views

Delay FIN-ACK sent on linux

For a project I need to delay the FIN-ACK sent in an SSL connection on Linux. Is there any way to do this? I can send an https request by using curl https://www.google.com, but how do I modify the TCP ...
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4answers
647 views

Writing a TCP server in bash [duplicate]

So, I recently found out about how you can send TCP packets through the /dev/tcp/hostname/port file, but my main problem here is how I receive them. I want to make a bash script that can host a TCP ...
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How to limit my bandwidth at linux? [duplicate]

which parameter I need to configure at "ls /proc/sys/net/ipv4/tcp*" to limit my bandwidth to receive less packages from my TCP connection?
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58 views

SIGSEGV: 0x0000000000000000 in ?? ()

I am executing an iperf connection between two UML machines running the following kernel: Linux client 4.1.0-ga61e56d #55 Mon Nov 30 13:51:59 CET 2015 x86_64 GNU/Linux I am working on the TCP/IP ...
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2answers
45 views

tcpdump bassed datalogger

I am building a datalogger with raspberry pi. I have used a Shell script in rc.local, I am capturing the bytes using tcpdump. The Problem am facing is that the log file is getting replaced each and ...
0
votes
3answers
1k views

open port 8080 for listening

My question is very simple, how can I open 8080 port for listening? In normal situation, I have tomcat7 that listens on port 8080. sudo netstat -tanpu | grep ":8080" tcp6 0 0 ...
10
votes
1answer
1k views

/dev/tcp not found

When I try to run the following command: echo -e "GET / HTTP/1.1\n\n" | /dev/tcp/74.125.225.19/80 I get the following error message: bash: /dev/tcp/74.125.225.19/80: No such file or directory ...
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1answer
33 views

How do I store the data in disk directly in kernel module? [closed]

I capture the TCP packet in function of netif_receive_skb , I want to store the playload of TCP packet. we can't read/write the file in kernel module, so store in disk directly maybe a way? ...
0
votes
1answer
73 views

How to load balance mutiport traffic using HAProxy

I have 2 servers that host an application that listens to mutiple ports. Is there a way to load traffic between these servers using HAProxy? I tried this in configuration, but it didn't work: ...
0
votes
1answer
90 views

How to force TCP packets to use a specific NIC

My Linux (kernel 3.17) computer has more than one NIC: eth0, eth1, (and/or eth2...) I have several PC connected to each of them: PC0 <---> eth0 (192.168.1.100) PC1 <---> eth1 ...
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votes
1answer
169 views

Why are IPv4 TCP connections showing as tcp6?

Here's the output of netsat -tupn on my Debian Jessie server: Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program ...
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184 views

does NFS overrides TCP keepalive time?

NFS server somehow disconnect NFS client detect server is disconnected client tries to reconnect server reappears and reconnect successfully it seems that TCP keepalive, connection timeout is ...
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4answers
120 views

Is any solution to make interactive TCP/UDP server under Linux?

I need some tool like this one for Linux. I need not a GUI (i.e. GUI/CLI -- this is not so important), but I need to be able to make a server which can listen at any port, receive and send a raw (i.e. ...
3
votes
1answer
62 views

How to call lsof properly to retrieve all TCP connections?

# lsof -n -itcp | wc 92 919 10212 # lsof -n | grep TCP | wc 2482 27222 373861 What I'm doing wrong with lsof -itcp ? Such calling is skipping part of connections, looks like this ...
2
votes
1answer
37 views

Alternative of ArpRetryCount in CentOS

ArpRetryCount Implemented by Microsoft and the following is its descritption : Determines how many times TCP sends an Address Request Packet for its own address when the service is installed. ...
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1answer
48 views

Iptables dropping HTTP 302 packages contain suspicious domain string

The HTTP 302 packages I want to block have: Header HTTP/1.1 302 Found Location: ...