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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Using socat to Tunnel/Proxy TCP want to split send/receive into separate files

I'm using socat to dump plain TCP (e.g. HTTP) traffic: socat -v tcp-listen:$PORT,reuseaddr,fork,keepalive tcp:$TARGET_HOST:$TARGET_PORT At the moment all send and receive traffic is dumped into ...
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368 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 ...
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668 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 ...
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46 views

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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46 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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30 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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40 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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215 views

Difference between MTU for a route and MTU for an interface

There is a server I connect to over the WAN and somewhere over the route there is packet loss unless I set the interface MTU to 600: ifconfig eth0 mtu 600 Doing this causes problems with ...
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242 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 ...
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431 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: ...
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123 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 ...
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257 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
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0answers
150 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
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0answers
533 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 ...
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93 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 ...
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25 views

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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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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69 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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82 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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145 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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60 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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108 views

How to download a video from rtmp protocol from behind proxy using rtmpdump

I am trying to download video from rtmp://flash.dce.harvard.edu/bounce/mp4:2015/01/14328/L01/14328-20140902-L01-4-h264-av1248-16x9-852x480.mp4. My college internet runs behing proxy, Is there a way I ...
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131 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 ...
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88 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 ...
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139 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 ...
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134 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 ...
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620 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 ...
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433 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 ...
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707 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. ...
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91 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 ...
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61 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 ...
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20 views

Cannot telnet outside network to open port on OEL 6 machine

I have an OEL 6 server that locally is assigned IP 10.200.15.79. It is hosting a business application that uses port 1031 to send and receive information through TCP/IP. To allow this on the OEL ...
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52 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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40 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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19 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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9 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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34 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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23 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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21 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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14 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 ...
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118 views

How do I increase my network perform on Centos 7

I am doing some research and I find that I have to configure the sysctl.conf file if I want to increase the network performance. So, I want to configure the default maximum Linux TCP buffer sizes ...
0
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0answers
104 views

Too many “ESTABLISHED” connection

I have a setup where my client talks to the server via CORBA connection. Both client and server runs on different machines. When I start my client a connection is "ESTABLISHED" with the server. Once ...
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89 views

Optimizing kernel TCP stack / parameters for services running on one host and communicating over TCP

I have a dual server {} block setup for my webapp running on nginx. For learning purposes I want to play around with performance tuning: Questions: What happens to a request going from one server ...
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327 views

Transparently Relay TCP Socket to Serial Port (and vice versa)?

I would like to create a pseudo serial device (such as /dev/ttyXXX0) that I can use to make transparent serial connections to an Arduino that's on my WiFi (via an esp8266 serial bridge). I would like ...
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498 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 ...
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150 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 ...
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124 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 ...
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186 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 ...
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103 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?
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224 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 ...