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 can I see 127.0.0.1 traffic on Windows using Wireshark?

Every time I try to filter to just show a specific IP address, I get an error indicating that it is "not an interface or a field." I have no idea what that means. Furthermore, I don’t really see any ...
2
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3answers
43 views

Meaning of netstat output?

When I type "sudo netstat -an", this is part of the output I get: Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 192.99.202.17:39922 ...
0
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1answer
17 views

What is the master process running on port 465?

I want to close non used ports in my server, after doing a port scan I found service urd running on port 465. Running lsof I see a "master" process running on that port (also 25, 587,etc..). Question ...
3
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1answer
48 views

TCP throughput much better than UDP

I'm monitoring the performances of a WAN link with iperf between two windows machines on both ends. Surprisingly (for me), TCP single session default window reaches a throughput of 12Mbps, while UDP ...
0
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1answer
2k views

OpenVPN working with TCP not with UDP

I have successfully set up an OpenVPN server on Debian (raspberry pi model b+). With the protocol set to TCP it works exactly as desired (internet routed through VPN, access to local network machines),...
0
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1answer
307 views

Which of the following protocols can use multiple TCP connections between the same client and the server?

In one of the pairs of protocols given below , both the protocols can use multiple TCP connections between the same client and the server. Which one is that? HTTP, FTP HTTP, TELNET FTP, SMTP HTTP,...
1
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1answer
39 views

Connect Linux boxes in IP over USB

I went through The best way to do TCP/IP over USB on Linux?, and would like to know more about the feasibility/procedure in order to have two Linux boxes IP-talking to each other over USB. I did it ...
0
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1answer
6 views

“Follow TCP stream” inserts extra line breaks and strings like “2000” “a7c” “0” (chunking?), how to hide that?

I often use "Follow TCP stream", very convenient to see the whole client/server conversation. PROBLEM: Some strange characters (that are not in the real packets) are shown. Maybe due to HTTP chunking?...
2
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0answers
165 views

What is the full process of a client downloading a torrent file?

I'm attempting to write a torrent client, and while the unofficial specification is quite helpful on a technical level, I would like an explanation of the process of downloading a torrent file (...
0
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1answer
26 views

Why are there ESTABLISHED packets without preceding SYN_SENT or SYN_RECV

I open two side to side bash widnows one with : netstat -anutpc | grep ESTABLISHED | grep kde the other with netstat -anutpc | grep -e SYN_SENT -e SYN_RECV, I start konqueror and go on youtube. I got ...
3
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1answer
107 views

iptables reject tcp-reset on loopback

I am trying to check how a software would behave if there is a network failure. That software is using tcp send() and recv() to communicate. Previously I was making the software communicate by ...
5
votes
3answers
9k views

Cannot connect to guest OS from host OS

I have installed OpenSUSE on VMWare player as guest OS and my host OS is Windows XP. What I want to achieve is to send message from my host (i.e XP), say on port 7000 and receive it on a specific port ...
2
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0answers
74 views

How do I kill existing network connections on Linux?

I've been working on a project that is nearly complete: to be able to kill my children's internet connections at the touch of a button. I've implemented part of the solution by basically calling: ...
0
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1answer
32 views

Download very large files with HTTP

I'm downloading the PlaceNet compressed database of place images (~132GiB). Unluckily the downloaded file is corrupted. I have tried several times, each time the extraction is stopped at different ...
1
vote
1answer
22 views

netem packet loss for packets destined to the same machine

I am using a command like sudo tc qdisc add dev eno1 root netem loss 10% to delay all the outgoing packets over the interface eno1, but this won't work if the packets are destined for the same ...
20
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2answers
36k views

What does SSH use UDP for?

Wile doing research I noticed that SSH both uses TCP and UDP. I completely understand the use of TCP, but UDP seems a bit strange. Why would I use an "unreliable" transport protocol with minimal ...
0
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1answer
116 views

ping works but iperf3 doesn't show any traffic for TCP

machine A has IP (eth0: 192.168.1.1, eth1: 10.10.xxx.yy) machine B has IP (eth0: 192.168.1.2) A and B are connected through RJ5 on eth0, both sides. ping works fine on both side, but when running ...
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0answers
23 views

Windows 10 tcp timed out

Few time ago my notebook with win 10 started behaving strange. My Google Chrome always give me ERR_CONNECTION_TIMED_OUT for something about 5 or 10 minutes and then start to work normally. I've also ...
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1answer
51 views

TCP socket buffer for every flow

Does the linux kernel create a buffer for every TCP connection, for example when we have 1000 tcp connections the kernel creates 1000 socket buffer and stores the packets of individual flow on its ...
10
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5answers
85k views

Open a test TCP connection to a specified IP/Port

I'm looking for a tool that works across windows (xp through 7) that will allow me to open a TCP connection to a specified ip and port. This functionality used to exist in windows xp (netsh diag ...
2
votes
4answers
1k views

Easy-to-use program for directly transfering big files to an IP-address

I saw this xkcd comic and was horrified that he is actually right: xkcd comic So, is there an EASY program to share files directly over IP? In the spirit of: open it it displays your current IP ...
6
votes
4answers
17k views

TCP Retransmission vs. TCP Fast Retransmission

In Wireshark I can see things that say "TCP Retransmission" and "TCP Fast Retransmission." What's the difference? How is Wireshark able to tell the difference?
0
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1answer
29 views

how can i get SYN & SYN+ACK value for current tcp connection of any website on Browser?

As I know that '$sysctl | grep net.ipv4.tcp' gives the system wide TCP parameter value,I need to make a script in Bash for my college practical file in which If we open Browser and input the ...
1
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1answer
31 views

What are the default nmap options?

Which options are used by default, when the user fires # nmap target without any explicit option? I am going to write the defaults of the three options I consider the most important. It would be ...
3
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2answers
61 views

IPTables - Redirect traffic based on country

Is there any way how to allow TCP traffic only from specified countries on a specified port and the rest of traffic redirect to another IP/port using iptables ?
2
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1answer
38 views

How get the value of TCP connection establishment timing,retry timing in ubuntu 14

how i get the value of TCP connection establishment timing ,retry timing for any TCP connection and also Quality of services parameters in Ubuntu .
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3answers
121 views

Why do computers have 65,535 TCP ports? [closed]

Why do computers have 65,535 TCP ports? Where does this number come from? What does it represent?
1
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1answer
16 views

Tcp Re-transmission timeout in a very short time?

I have two Windows 2012 R2 machines (122 and 115) hosted on the same VMWare host. We have a heartbeat at application layer between those two machines, from time to time there will be tcp re-...
1
vote
1answer
54 views

Wireshark's reassembled PDU consists of TCP segment size > MSS?

I'm looking into a Wireshark record provided by someone, to analyze something for them. Wireshark has conveniently reassembled 3 TCP segments that all transported a single TLS packet. The TLS packet ...
0
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1answer
24 views

TCP connection with multiple proxies in between

Client sends an Proxy-Connection: Keep-Alive header, the intermediate smart proxy sees this header and replaces it with Connection: Keep-Alive and sends to the web-server. All good and fine. What if ...
1
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1answer
29 views

are TCP connections made while typing the URL

Do browsers make TCP connections while typing the URL in address bar? I launched nettop utility, and was surprised of how active my connections are, even while only typing an address and not visiting ...
1
vote
2answers
56 views

RST sequence number and window size

RFC793 states the following about RST processing: In all states except SYN-SENT, all reset (RST) segments are validated by checking their SEQ-fields. A reset is valid if its sequence number is ...
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0answers
25 views

Strange response from a HTTP server

I noticed an unfamiliar device when scanning my local wireless network. It had two open (listening?) TCP ports; TCP/80 (http?) & TCP/443 (https?). In an effort to identify the unfamiliar device;...
0
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0answers
17 views

Unable to find traffic for specific device w/ Wireshark (over Wi-Fi)

I have a device communicating with a TCP server running on my machine. My machine is normally connected to the network via ethernet, however I also have a wireless adapter that I can use to connect to ...
0
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0answers
19 views

Direct host SMB - Ports

It's well known that SMB uses port 445, and that NetBIOS uses ports 137-139. However, according to all official MS documentation (https://support.microsoft.com/en-us/kb/204279), SMB uses both TCP and ...
0
votes
2answers
753 views

How can I remap outgoing TCP ports?

Is there any way to remap a TCP port from a program were you not can change the port number? The program talks on port 4321 and I want it to go out on port 14321 on the local computer.
0
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0answers
40 views

TCP congestion control

I was curious to know which are the default TCP congestion control method used in latest version of MacOSx, linux kernal, windows 8, windows 7 and windows xp. Does it use newreno or anything newer?
0
votes
1answer
22 views

DrayTek Vigor 2830 open port issue

We're using a Vigor2830 for routing VoIP/SIP traffic. One of the ports required to be open is 5090 for TCP/UDP. Going into the open ports section of the Vigor menu we have opened all the ports ...
1
vote
1answer
875 views

Can IPSec (or any other VPN tunnel) hide your IP address while browsing?

Is there a VPN/tunnelling method which you can use to browse the web, but will also prevent somebody from seeing your IP address if they were sniffing the network? I wasn't sure if the IP address ...
13
votes
5answers
18k views

How do IP answer packets reach their destination inside of a private LAN?

This is a little theory question that has been confusing me for a pretty long time. Basically, if we are inside of a private LAN, and we want incoming packets to reach, for example, an HTTP server ...
2
votes
2answers
143 views

Send TCP with incorrect checksums

I'm having trouble sending large files to an OpenStack machine. Our Internet connection is over LTE so bad packets are to be expected. However, even sending data over TCP results in corrupted data ...
0
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1answer
11 views

Reason for TCP Slow Start in Subsequent Connections

From my understanding TCP slow start is used to compensate and prevent congestion and loss. When a connection is successfully established and used for a while, the bandwidth of the TCP connection is ...
0
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0answers
11 views

pfSense does not close connections coming from LAN

I created a NAT rule that redirects external_ip:1234 of modem (pfSense itself) to 192.168.1.100:1234. I also wrote a server application which listens for connections on 192.168.1.100:1234. When I ...
0
votes
2answers
34 views

TCP: Disable pure ACKs?

I have a scenario where I wish to disable pure ACKs (TCP ACKs with no data), but I can't find how to do this. Is there an option that I can set so that ACKs are always piggybacked onto the next data ...
0
votes
1answer
106 views

Socat not closing tcp connection

I use socat 1.7.3.1-r0 and run following command on an alpine 3.3 linux server: socat -d -d -d PTY,link=/dev/ttyFOOBAR,echo=0,raw,unlink-close=0 TCP-LISTEN:7000,forever,reuseaddr Socat will listen ...
0
votes
1answer
16 views

Connecting from WAN to LAN

I'm developing an app for my family that uses sockets to comunicate between devices in LAN or WAN. As IP addresses change constantly I am planning an FTP server for address book and TCP/IP for ...
2
votes
0answers
349 views

Tunnelling TCP connection through NAT

My server is in my school's NAT and my desktop computer is in my home NAT. I want to SSH to my server from home. I normally used school's VPN, but recently for some reason I can't. So I'm looking for ...
2
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4answers
21k views

Subnet mask of 255.255.255.255

I have a subnet mask of 255.255.255.255.( Why is my subnet mask 255.255.255.255?). I refer that from the above question that it is as good as each computer is on its own network and cant interact with ...
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2answers
78 views

Why game latency fluctuates aggressively during day?

I play World of Warcraft (uses TCP) from India, on a server located in France. I get 180-200ms in-game past midnight which is quite comfortable for me, and unfortunately the best I can get due to the ...
-1
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1answer
40 views

TCP RST Connection - Netflix - Only on Linux

I wouldn't have asked this here, but I am at wit's end, this makes absolutely no sense at this point. I have been trying everything. I have a single iptables rule: -A POSTROUTING -o eth0 -j ...