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 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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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
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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 ...
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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 :::...
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/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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39 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? ...
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102 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: ...
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158 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 (192.168.1....
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1answer
524 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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263 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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135 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. ...
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74 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 ...
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42 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
60 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: http://www.yxjiaodai.com/ad/?id=1023&url=http%3A//a1819.oadz.com/link/C/1819/3081547/dtMdon4l79FwsIo2JXEHqtdp5eQ_/...
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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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2answers
44 views

Using remote XServer

I recall seeing a tutorial on setting up Xorg to be a vnc replacement without installing anything, but I cannot find it. I was hoping someone here could help out. Scenario: Machine A no monitor ...
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142 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 ...
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1answer
568 views

Why do I have Established TCP connections with no owner PID?

Both ss --processes and netstat --program (with sudo) list some ESTABLISHED TCP connections to local port 6514 with non-zero Recv-Q values and no owner process (netstat output shows - where PID/...
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1answer
743 views

Read “/proc” to know if a process has opened a port

I need to know if a process with a given PID as opened a port without using external commands. I must then use the /proc filesystem. I can read the /proc/$PID/net/tcp file for example and get ...
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3answers
487 views

Why do some TCP reset packets show up in my iptables log?

I started to add some basic iptables rules on my Debian Jessie server. My objective is to filter and log network traffic (for security and learning purposes). Disregarding ICMP packets, these are ...
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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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How were these Linux TCP default settings decided?

I spent quite some time tracking down a problem in production recently, where a database server disappearing would cause a hang of up to 2 hours (long wait for a poll() call in the libpq client ...
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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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375 views

Distinguish TCP server from client within netstat output

I have a socket connection between a client process and a server process, both running on my machine. There are two entries shown for the connection as, sudo netstat -ntp | grep 56442 tcp 1 ...
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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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How to create a TCP listener?

Introduction: I have created a bash function that is able to check whether a port is available and increments it by 1 if false until a certain maximum port number. E.g., if port 500 is unavailable ...
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167 views

Effect of limiting tcp connections through iptables to limit ssh sessions

I have limited no. of tcp connections through iptables to limit total number of ssh connections. Now when i am adding a rule with maximum limit of tcp connections lesser than currently opened ssh ...
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2answers
939 views

How to use lsof to identify incoming TCP connections?

I want to know if my server establishes a connection to a remote server or if the remote server tries to reach my server. I tried to read the output of lsof and obtain this information: lsof -i TCP:...
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359 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 ...
3
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1answer
5k views

Changing the TCP RTO value in Linux

I want to alter the TCP RTO (retransmission timeout) value for a connection, and some reading I have done suggests that I could do this, but does not reveal where and how to change it. I have looked ...
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701 views

Meaning of 'netstat -anto' output

I did netstat -anto and got following result: Proto Recv-Q Send-Q Local Address Foreign Address State Timer tcp 0 0 127.0.0.1:1169 127.0.0.1:...
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Linux kernel parameter “net.ipv4.tcp_workaround_signed_windows”

I am seeing some intermittent network issues when sending large amounts of data over a network and it has been suggested to me that setting this option to a 1 may possibly resolve the issue. ...
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125 views

What ports will an ssh daemon use outbound?

I am making a bastion ssh server. When I use the following rules in its ip tables, I am able to connect to the server just fine: Inbound Rules Allow traffic on port 22 from my client's IP Block all ...
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96 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 ...
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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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1answer
144 views

How to enable SYN Cookies on Debian 7.5?

How do I enable SYN Cookies on Debian 7.5? nano /etc/sysctl.conf #net.ipv4.tcp_syncookies = 1 remove here the # sysctl -p service network restart Is that the correct way? Or what must I look at?...
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1answer
94 views

Unexpected netstat output in DNAT conditions

So, here I have a basic setup with SOCKS5 proxy listening on, oh, say 8123 I redirect TCP to the proxy via iptables From iptables perspective everything looks peachy, iptables -t nat -v -L shows ...
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265 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 socket,...
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138 views

check tcp packets reception below tcpdump level

I am having an issue with my smartphone device and packets monitoring: I am trying to find a reason why I cannot establish a VPN connection via PPTP protocol. I have the following successful scenario:...
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1answer
111 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 OK....
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265 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?
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493 views

How can I edit /proc/net/tcp?

I need to edit 1 line in /proc/net/tcp while the file is also used by the linux kernel for updating other lines of it by the kernel. Background: Each line in /proc/net/tcp represents a TCP socket. ...
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105 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 ...
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2answers
401 views

Different Congestion Control algorithms in FreeBSD

Is there a way I can run a different (than the default) TCP congestion control algorithm in FreeBSD? I am trying to modify an existing TCP congestion control algorithm with some ideas published in ...
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1answer
667 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 ...
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tcpdump captures network-wide UDP traffic, but not TCP

When observing traffic with sudo tcpdump udp, it behaves like it should: I can see all traffic which is happening in the network, even when the machine which I am using is not involved. However, when ...
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1answer
213 views

Close the neccessary Ports [duplicate]

I am using Linux Mint and I am newbie. Someone is trying to access my computer via my MAC Address and open port. I have some questions: I know that there are different type of port like TCP and UDP. ...
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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 connections....
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3answers
4k views

Tool to generate TCP traffic

I want to generate a TCP traffic starting from the port 0 to the port 65535. 1 tcp packet for each port with 1ms between 2 packets. The generator should not care if there is a TCP ACK or not. Are ...
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2k views

D-Bus authentication and authorization

I'm trying to set up remote access to D-Bus, and I don't understand how authentication and authorization are (not) working. I have a D-Bus server listening on an abstract socket. $ echo $...