TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.

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How do you force linux to treat a tcp packet as if it were at the destination ip?

The situation: A tcp packet arrives on eth0 with destination 8.8.8.8. This packet meets some criteria that makes me want to intercept it (lets say I am interested in all packets from source ...
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HAProxy resetting backend connections [migrated]

I'm in the process of setting up a series of servers as proxies to our application server, primarily to obscure the application server's IP as part of a suite of anti-DDOS measures. My goal is to ...
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1answer
10 views

Forward TCP packets by destination and port number

Is there any way to forward only TCP packets heading to destination XYZ and port number NN to 127.0.0.1 port number 9150 ? I'm on Windows. Thanks
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20 views

RPC Connection Filtered with no Firewalls

I have a workstation (PC1) that cannot communicate with a domain controller over RPC (TCP/135). C:\PortQryV2> portqry.exe -n 192.168.1.1 -p tcp -o 135 Querying target system called: 192.168.1.1 ...
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42 views

Receive encrypted string from server [closed]

What is the easiest way (as easy as possible) to make a web server that will check a string received from client and respond with another string? How to do it from the very beginning to the very end? ...
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22 views

Which congestion control algorithm is used by the TCP stack in OS X?

What congestion control algorithm is implemented in TCP in OSX 10.9? I would like to know if it uses NewReno, or something newer like Cubic in Linux.
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Force local packet pass trough the router (or disable loopback) - windows 8

i would like to avoid that packets sent from my machine to the same machine (via the IP assigned by the external router eg. 192.168.1.20) are routed with loopback and so never reach the external ...
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20 views

How to split pcap files maintaining tcp sessions

I have a pcap file which contains tcp traces. I was wondering if there's a way to split these traces in order to maintain tcp flows, but also filtering the traffic on a src ip basis. For example, if ...
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3answers
71 views

What happens when 2 hosts simultaneous establish a connection in a 3-way handshake

Say two hosts, A and B, both attempt to start a connection with each other, but the SYN from A gets to B before B's SYN arrives at A. My answer is that A would sent SYN ACK and would ignore the SYN ...
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1answer
166 views

Localhost tcp throughput performance differences

I have been using psping for measuring bandwith statistics on localhost on different computers: laptops, home computers and servers. All of them get to between 100 and 200 MB/s but my PowerPc at work ...
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1answer
35 views

What is the timeframe used, for TCPBacklogDrop value calculation in netstat [closed]

I'm interested in the value TCPBacklogDrop of the command netstat -s on linux. But I don't know which timeframe is considered, when calculating it.
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39 views

Changing TCP sliding window behaviour

We all know that TCP's congestion control uses additive (linear) increase and multiplicative decrease when adjusting sliding window size. Is there a way to change it to "linear decrease"? When a ...
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1answer
25 views

Testing DNS truncated queries over TCP with dig

I want to test if my network supports EDNS0. It means that if the record is bigger than 512byte, the DNS will be over TCP. It will ne truncated at firts using UDP ,the it willbe over tcp. I'm using ...
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34 views

Cannot open port 25565 and others

I try to open my Minecraft server and my gmod server ports. Now I only try Minecraft and I tried to open in 192.168.1.1 in Windows firewall. I went to this site: ...
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1answer
34 views

Sending large data over TCP and progress indicators

It is my understanding that when you open a tcp connection to send data the tcp layer on the receiving end holds on to all the packet until the transmission is complete, then sends all the data up to ...
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28 views

Windows 7 stops responding to my SYN requests unless I continue to ping the client

Basic synopsis, my Windows 7 box stops sending RST, ACK packets to a client which is sending SYN packets after time. What I know: I have a client who sends a SYN packet, followed by a retransmit 3 ...
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1answer
36 views

How to determine which clients are connected to a specific port on a server [closed]

The network is Microsoft Windows but the server is running an unknown operating system. I cannot get access to a command line on the server. The server is running a custom protocol. The network ...
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1answer
32 views

Can I ping a host that has disabled the ICMP Ping option?

I need to know if it's possible to compare and test how fast is an IP (ie: any web or game server) relative to my location (in terms of network latency), even if they have disabled ICMP/Ping requests ...
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1answer
37 views

Different servers on the same port ipv4 / ipv6

Say I have two TCP servers A and B. A is an ipv4-only server listening on 127.0.0.1:10000. B is an ipv6-only server listening on ::1:10000. Can I start these on the same machine? That is, how are IP ...
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65 views

Retransmitted TCP packets (smaller than original) are being dropped, causes hang

I'm trying to troubleshoot my home internet connection, which often hangs on large downloads. I believe I have been able to duplicate the problem between my home computer and an Amazon EC2 instance ...
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1answer
41 views

TCP server listen and client listen windows software

I am using Windows OS on an amazon cloud AWS with static public IP. On this machine I need to set up a TCP server to listen on port 2204 for raw data that will arrive from a GPS base station over TCP ...
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83 views

Forcing a game to not take “real local IP” into account but only recognize virtual local IP assigned by VPN server

We are two friends who want to play Heroes of Might and Magic 2, 3 or 5 together in online multiplayer mode over internet using a TCP/IP connection. As we are not happy with third party solutions ...
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How does a server get notified about the HTTP request?

I have a basic understanding of how HTTP works. I understand the client (web browser) makes a request and server responds back to the request. However, the thing I don't understand is how does a web ...
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26 views

Window Period Where Sent Packets Cause Socket Acting as Server to Malfunction

I am currently working on an embedded Linux server. My main application is a state-machine that is started during the init phase from the rc-scripts. The application spawns several worker threads. ...
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3answers
78 views

How does a web server return an HTTP request?

I'm sorry if this is a really stupid question; my networking knowledge is pretty sparse. So, a user makes a HTTP request to some address. That request comes from an address on a local subnet, but the ...
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Assessing Performance in Process Explorer: Varying Block Sizes

I am trying to assess the performance of my scientific software using Process Explorer, with the files both locally on our blade server (Dell VRTx, Windows Server 2012) and over the network from ...
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1answer
96 views

Accessing two devices with the same IP?

I want to connect my laptop to two WiFi enabled digital cameras, that have the same IP hardcoded: 192.168.1.1 One solution that I've successfully tried: Connect one device to the laptop's built in ...
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1answer
142 views

Cannot connect to 192.168.1.1

I have router TP Link n900 and I cannot connect to my admin panel of the router, I just bought it, I have internet when I am connected with cabel, but cannot open the router. My connection is : PC -> ...
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How does HTTP become stateless?

HTTP is said to be stateless. Meaning, it doesn’t need to store information for the transmission of data. But HTTP uses TCP, which is state oriented. If that's the case, how does HTTP becomes ...
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28 views

Network tcp parameters

i have a netstat -s output which i would like some opinions on. Which are the parameters that seems to appear to have problems? from what I can see, tcpInUnorderBytes and tcpInUnorderSegs have some ...
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1answer
74 views

Keep alive, ESTABLISHED and TIME_WAIT semantics

When I use the following command netstat -ant | grep :9111 | awk '{print $6}' | sort | uniq -c | sort -n I get the following 1 LAST_ACK 1 LISTEN 2 SYN_RECV 7 FIN_WAIT1 51 ESTABLISHED ...
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3answers
84 views

TCP connection assistance

I have 2 PCs at home connected to a router. I am trying to establish a TCP connection from PC2 to PC1. I have installed TCP Test Tool 3.0 on both and have set PC1 to listen on port 54100. On PC2 I ...
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101 views

Does an open TCP socket connection consume data when not used?

I have a TCP socket connection established between my server and a modem which has a active GSM module and sim card installed. I create this wirless 3G connection via socat: /usr/bin/socat ...
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What's wrong with this tcpdump syntax?

sudo tcpdump -i ath1 -s 0 -nne "(type mgt and subtype beacon)" Can anyone help me? I was following a tutorial at http://wiki.secarmour.com/2013/09/capture-wireless-traffic.html but seems I got ...
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127 views

TCP/IP to Serial - Serial Server

I have a server with 8 COM ports which I would like to make accessible via TCP ports, I've done quite a bit of research and tried numerous solutions including ser2net etc. All of which unfortunately ...
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2answers
51 views

TCP Client and Server Port forwarding

I have a TCP client and server program that I made. My question is, when running the client and server on two separate machines that go through a different firewalled router over the internet, does it ...
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1answer
125 views

Port forwarding and C++ Winsock Client-Server applications

As the title says, I'm creating a TCP client and a server program in C++. My question is, when running the client and server on two separate machines that go through a different firewalled router over ...
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1answer
74 views

A tool for sending and receiving plain text via TCP? [closed]

For debugging purposes, I'm looking for a tool that can do the following: Connect to a TCP socket send plain text commands receive plain text answers Yes, of course telnet can do that. But my ...
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159 views

Disable TCP keepalive on RHEL6

Is it possible to disable TCP keepalive on RHEL6? I know the kernel parameters for tuning TCP keepalive timeout are as follows: net.ipv4.tcp_keepalive_time net.ipv4.tcp_keepalive_intvl ...
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60 views

Create local TCP connection from C program in Ubuntu VM to Labview in Windows (Host)

Sorry if this is lengthy, I'll try to keep it as concise as possible. I have made a C program which runs in Ubuntu in a virtual machine and a Labview program running in windows (the host of the VM) ...
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80 views

netsh set autotuninglevel: “the parameter is incorrect”

When trying to do netsh int tcp set global autotuninglevel=disabled from a command prompt, I get the error message "The parameter is incorrect". Several search results suggested "disabling 64-bit ...
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Using DJB's tcpclient or tcpcat bidirectionally

Can someone post an example on how to use DJB's tcpclient bidirectionally? We need to read from Tor's ControlPort as well as write to Tor's ControlPort. A "file" that is open for both, reading and ...
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113 views

Can't capture inbound/outbound messages in Fiddler

.NET interferes with localhost traffic (there's already a lot of threads open on that topic), but something else is mangling my ability to see traffic to/from my server. I know this because I am ...
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29 views

TCP 'ip route change' not working to change cwnd on Linux

I'm trying to change the cwnd using 'ip route change'. The command I'm using: ip route change 172.16.231.0/24 dev eth0 proto kernel scope link src 172.16.231.26 cwnd lock 7. The first time I run ...
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143 views

not all packets forwarded by pptp VPN server

I have the following setup: +------+ +---------+ ppp0---------+ |router| | A +-----+---+-----+ B | | R | ...
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1answer
89 views

Reverse SSH Tunneling Question [closed]

I'm somewhat confused on reverse SSH tunneling and I'd really like someone to help me out. My Goal: I'd like to create a physical backdoor to a network using a BeagleBone Black (or RaspberryPi or ...
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180 views

virtualbox: no TCP traceroute

I have VirtualBox running Ubuntu on an Ubuntu host. The networking mode I set is NAT. I noticed that TCP traceroute-like messages (i.e. with low IP TTL) never receive any ICMP reply. Is there some ...
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2answers
89 views

Is the Transport Layer (e.g. UDP, TCP) handled by the Operating System usually? [closed]

I'm really new to networking and am struggling to understand this. I know the Transport Layer in the Internet Protocol Suite (at least the UDP and TCP protocols) contains the source and destination ...
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107 views

Connection Oriented Transport Protocol

Does anyone have an idea about a software for Linux that uses COTP (ISO 8073) protocol ? note : software that runs COTP over TCP , doesn't matter what is the functionality of the software i just need ...
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2answers
111 views

How do I delay tcp traffic on a socket?

I would like to test the interactions between a client program and a server program for race conditions. They connect to each other via tcp. The client does blocking calls to the server on multiple ...