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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Connection interruptions on Debian router, possibly due to excessive duplicate ACKs?

I have a Debian server as a house router, which for a year has been working flawlessly. However, I recently moved and switched service providers from FiOS to Comcast, and possibly as a result am ...
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1answer
43 views

Decrypt SSL at the TCP level

I'm trying to decrypt SSL at the TCP level for data that I'm sending to a remote server. The reason I'm doing this is because the remote host intermittently sends me RSTs, and I'm trying to identify a ...
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20 views

Create SSL TCP connection with java code to send string data [on hold]

I am trying to performance test a server that uses SSL TCP socket communication. Need to send a string data to the server and validate the response back. Is there any way to perform this with java ...
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1answer
25 views

TCP socket communication from client to server

I am trying to test the performance of a client/server application that uses TCP communication. If I trigger multiple requests from the client, would it flow through the same connection/pipe to the ...
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0answers
6 views

Route only on output chain?

I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
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4 views

iptables block access to all ports except 53 (tcp,udp) from one IP address

how can i block all ports from one IP address except the port 53 TCP,UDP? example: ip 192.168.0.15 access only port 53 (udp,tcp). thank you.
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16 views

How to tunnel UDP traffic over Tor?

I know that Tor does not support UDP for now . But I came upon certain application Onion Cat .But I don't know if it work or not . Is there any other procedure ? Is that even possible ? Please guide ...
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37 views

Possible .NET Issue - Exception Thrown in C# Code [migrated]

I was directed to SuperUser from a question I posted on stack overflow. Link to StackOverflow question: New Instance of TCPClient Exception While creating an application on Visual Studios 2013 ...
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17 views

Simultaneous TCP Keep Alive requests no second ack

I have a TCP server running on port 6524 and a client running on port x11 on the same system (Linux sys-111 2.6.32-431.29.2.el6.x86_64). Both these send TCP Keep alive messages to keep the connection ...
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2answers
142 views

Data retransmission and WSAECONNABORTED (10053) socket error

Say I have two sockets that are connected to each other (Socket A and Socket B). If the computer that have Socket B is unplugged from power, then if Socket A tries to send some data to Socket B, the ...
2
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1answer
93 views

ISP Issues - TCP Out-of-Order

Accessing any webpage (basically any TCP connection), results in multiple retries before and long loading times before it loads a page with missing elements (reload might fix it). Google Chrome throws ...
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2answers
51 views

Are FIN packets guaranteed to arrive?

In the 4-way handshake, we have the following: FIN -------> <------- ACK <---x--- FIN (what if this packet is lost?) ACK -------> What happens if the third packet is lost, will it be ...
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23 views

Monitor TCP port traffic and get a sound alert when a specific text string is found on Windows

I need to watch a port for several hours and make an audible alert whenever a specific string comes through. Windows only. Is this possible with Wireshark or another sniffer tool or maybe a sniffer ...
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1answer
51 views

How to share via TCP serial port CAT

I want to connect my amateur radio transceiver to a linux (Ubuntu) computer with USB cable (serial port (in windows should be COM3 or COM4) like /dev/??? ) and share it locally with TCP, Is it ...
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0answers
52 views

Should I disable Netbios over TCP/IP for printing throught Samba+cups?

I have a domain with 100+ machine which are reparted on two IP ranges. On this moment, computers are using netBIOS over TCP/IP or SMB over TCP/IP. It seem that two requests are send ...
31
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1answer
3k views

What happens to TCP connections when I remove the ethernet cable?

For a TCP connection, when I remove the cable and reconnect after 30-40 seconds there is no packet loss issues. But when the reconnect time is more than a few minutes all the packets are lost. I know ...
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5answers
757 views

What ports are used by an application [duplicate]

I'm testing an application which opens its own ports (acts as a server for these ports, hence listens at that ports) and where the same application connects to ports bound by other applications (acts ...
2
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1answer
32 views

Man in the middle using iptables

I wish to test a subsystems which communicates with another subsystems via tcp. I have used the following: "iptables -A OUTPUT -p tcp --dport "+port_number" -j DROP" to stop the traffic on a port ...
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2answers
125 views

If HTTP runs on a port, does that mean TCP can also run on that port?

I'm building an app that needs to run on a mobile smartphone over a GPRS/3G network. I'm doing bit ops, so every byte wasted through HTTP headers is bad. Mobile providers in my area make heavy use of ...
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0answers
35 views

What is the primary function of the transport layer in the Internet protocol networking code [closed]

I am not sure if I have answered this question right, so would appreciate it if someone could correct me. The question is: What is the primary function of the transport layer in the Internet protocol ...
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1answer
43 views

List all open sockets in /dev/tcp/localhost/

Is it possible to list all open sockets in /dev/tcp/localhost/ on a Linux machine? I want to list all sockets where the following command would return 0: timeout 2 bash -c "cat < /dev/null > ...
0
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1answer
72 views

VMware TCP port mapping not working - port not accessible via public IP address

Simply speaking, the forwarded port 45922 is accessible on the host via 127.0.0.1:45922, but not accessible on the host itself via its public IP plus port number 45922. Details are as follows. Host ...
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1answer
130 views

TCP congestion control Windows 7

Based on what I read, Compound TCP is disabled by default in Windows 7. If so, which default congestion control algorithm does windows 7 use? Is it TCP RENO or NEW RENO? Could you give me some links ...
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1answer
38 views

Wget not getting cookies, not pulling back results in check.

I'm having a couple of issues when porting check scripts between a couple of servers. The script. #!/bin/bash hostname=$1 port=$2 retstatus=0 retStr= st=`date "+%s.%N"` if [ $# -ne 2 ]; then ...
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2answers
57 views

How are Internet connections differentiated from each other by an operating system?

Given this example, how would my operating system differentiate between each request. Let us say I have 3 tabs open, and at the same exact time, they all go to http://google.com. How would my ...
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38 views

How can one redirect to a new host all traffic destined for an old host?

We're moving a bunch of services, say from 1.2.3.4 to 5.6.7.8. In order to test that the new services are correctly configured, we'd like to redirect (to the new host) all traffic destined for the ...
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1answer
69 views

Bittorrent client makes multiple connections upon its start to amazonaws

I have this weird situation that every time I open my bittorrent client application, upon its start, it starts to make a lot of multiple connections(more than thousands) to amazonaws servers and as ...
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2answers
307 views

TCP Dup ACK/Retransmission, bad configuration?

I'm currently investigating network issues of a friends LAN (again). The Internet connectivity is very slow and unreliable and sometimes services simply don't work. I've monitored the traffic for ...
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0answers
49 views

iptables TCP flags

I'm beginner with iptables and networking so please excuse me for such dump questions. I found in Internet part of filtering malformed packets: /usr/bin/sudo /sbin/iptables -A tcpchk -p tcp ...
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0answers
89 views

iptables TCP flags

I'm beginner with iptables and networking so please excuse me for such beginner questions. I found on the Internet part of filtering malformed packets: /usr/bin/sudo /sbin/iptables -A tcpchk -p tcp ...
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0answers
6 views

What happens when I terminate a process and the socket send buffer is not empty? [duplicate]

In Windows (and probably in other operating systems), if a process has a TCP connection with another process on another machine, and then I terminate the process, an RST packet will be sent to the ...
3
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1answer
98 views

What happens when I terminate a process and the socket send buffer is not empty?

In Windows (and probably in other operating systems), if a process has a TCP connection with another process on another machine, and then I terminate the process, an RST packet will be sent to the ...
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0answers
16 views

Determining whether a port is closed (no one is listening) or iptables reject my host

Can I tell whether the service I'm calling has a reject rule in its iptables or it doesn't listen on the port I'm calling? it seems that I always get icmp port unreachable
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1answer
25 views

3 duplicate ACKs in TCP

If a client receives 3 duplicate ACKs in TCP then it will half the window size and switch from slow start to congestion avoidance. Will it retransmit the next window_size segments, or will it just ...
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1answer
26 views

Multiple TCP Connections to download simple webpage and images?

I created a very simple webpage: <html> <body> foo bar <img src="img1.png"/> <img src="img2.png"/> <img src="img3.png"/> Hello world </body> </html> And ...
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0answers
28 views

Check if ports are open for talking

I have a software (HP BSM) installed in a Windows server 2008 R2 Std This software needs to "talk" through a specific list of TCP ports and "listen" through other TCP ports. How can I know/check if ...
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1answer
47 views

Why is the FIN flag in TCP called FIN?

There are some flags in TCP. I already understand what other flag names come from, such as SYN stands for synchronization. I also know that FIN is used to close a connection. What I don't understand ...
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1answer
34 views

HTTP performance over high latency links

I have users that previously used FTP for file transfers across high latency paths to their local server. They have switched to HTTP for these transfers (not by choice) and file transfer perforamance ...
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1answer
110 views

How to redirect TCP traffic from one virtual machine to another in Linux?

What is the simplest way to redirect all TCP traffic from one virtual machine to another in Ubuntu Linux and reverse? And what type of connection I suppose to use in VirtualBox?
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50 views

Tunneling trough VPN over TCP

I'm currently trying to set up a VPN on my server to connect to from my Laptop. The server is a command-line ubuntu running on a x64 machine. The Laptop runs x64 Windows 7. The VPN itself is already ...
0
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1answer
36 views

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 ...
0
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1answer
31 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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1answer
160 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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1answer
46 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? ...
0
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0answers
70 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.
2
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0answers
54 views

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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0answers
85 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
88 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 ...
3
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1answer
460 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
122 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.