Questions tagged [tcp]
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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QEMU: SYN/ACK ignored on host in host-only networking with tap interface
I'm trying to set up host-only networking between my Linux host (running Fedora 33) and a QEMU instance (a fork for Xilinx devices), more specifically between a bridge interface (host) and a tap ...
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socat resetting USB port on open
I'm having an issue with socat, and it is probably just in my environment.
I need to have a USB serial port redirected to a TCP port. I use the following and it works perfectly:
socat TCP-LISTEN:4444,...
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SSH file transfers slow with lots of TCP retransmissions
Good evening,
I use SFTP (File Transfer over SSH) from a computer (Windows 10) to a Synology NAS. Both devices are behind NAT on different locations. Around 3 weeks ago, whenever I initiated a ...
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Why do I get a "TCP Retransmission" right after having sent a packet?
I have a program (in Python) that publishes information to a bus (MQTT, implemented by mosquitto). This is a "fire and forget" kind of message, that is there is no long term subscription, ...
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After opening port 443 in windows firewall as inbound rule, I cannot see it when I run 'netstat -an'
As an inbound rule on Windows 10 firewall, I added port 443 as TCP connection allowing all types of connections. However, I cannot see it when I run 'netstat -an'. How can I get it so that I see my ...
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TCP port number reused
I am using STM32 TCP Echo server client Cube IDE example. I have server and client device. I can connect first time successfully but when I reset the client, I get after 70 line in wireshark ...
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Chunked HTTP response does not come through completely
Consider the following setup
+-------+ +--------+ +----------+
| | | | | |
| +----------->+ +---------->+ ...
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Modbus TCP Master-Slave
I have a problem with modbus master and slave TCP communication,
On windows computer:
When Master and Slave connect each other they communicate successfuly on 50905->502 ports, when I disconnect to ...
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How does the server get the correct MSS value in the TCP triple handshake
When the client establishes TCP connection with the server, it will report its MSS value during the third handshake. According to my understanding, the MSS value should be obtained by subtraction 40 ...
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TCP header option: SACK-permitted (Selective Acknowledgments) negotiation
I'm doing a research project, which needs to split tcp connection.
so I have some pecular questions, which may happen in my development.
The problem is understanding of TCP SACK-permitted negotiation....
CommunityBot
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is "Empty reply from server" a deliberate reply, or a default one from the TCP/IP stack?
I have a device whose port 80 is open and I was wondering what is behind:
~ # curl -v http://192.168.10.253 root@srv
* ...
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what is type of ICMP packets? TCP or UDP
The ping packet is a type of ICMP packet. Is there any relation between ICMP with TCP? In other words, can we guarantee their arrival in the network?
I want to know if ICMP packets in the network are ...
CommunityBot
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How to see all the TCP connections opened by Google Chrome browser on Mac?
I am currently browsing using the Google Chrome browser. I know that for every tab I open and type a URL in, a TCP connection is opened. I also know that a maximum of 6 concurrent TCP connections are ...
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java.exe opens up hundreds of ports on 127.0.0.1 on a windows 10 computer and listens to itself
After I ran netstat -ab with admin right on my win10 computer, which is not running anything "java" related on the desktop nor there is "java.exe" in taskmanager's "detailed ...
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eMule not connected
I'm using eMule v0.50a on Windows 7.
After installation, I clicked 'connect'
It is not connected.
Please see the attached screenshot.
It reads 'eD2K:Connecting, Kad:Connecting | Preparing'
How can I ...
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System error(10054) - An existing connection was forcibly closed by the remote host
I run a dialer made by Altitude Software. Few people are likely to be familiar with this product, so please bear with me.
Problem:
The Altitude dialer software is an application running on Windows ...
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Exporting TCP Connection Latency in Resource Monitor
In Resource Monitor in Windows 10 I am looking to monitor and log out the latency of for a particular TCP connection.
In Performance Monitor there is the option to create a data collector set but I ...
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Disable instant closing of TCP connections when interface or route becomes unavailable in Windows
Whenever there is a brief glitch with my ethernet connection, Windows 10 instantly closes all of my TCP connections going over that interface.
Is there a way to change it so that the connections are ...
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How to delete binded port from cmd in Windows 7?
How to delete binded port in Windows 7 from cmd? I'm developing client server application which running on the port 3434 and also is binded on port 0.0.0.0. When I type in cmd netstat -an, I get this ...
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understand ss -to4 output for a jdbc connection
My application connects to a database over JDBC, and performs a lot of sequential inserts. There is only 1 JDBC connection opened by the application. As the performance is not as expected, I started ...
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How to set different TTLHOP for TCP ports
We want to set sensitive TCP/UDP Ports at low TTL/HOP Leaving other ttl/hop at 128 default
data center = 3
Priv net = 8
Internet = 128 default
Ssh 22 = 8 (internal hop max)
Rdp 3389 = 8
Http 80 = 128 (...
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Why is TCP port 563 opened?
Can someone explain what service opens TCP port 563 and uses it?
I`m using Windows.
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Troubleshooting transport layer connectivity issues with pfSense
I am building a virtual network of vhosts that is NATed out to the internet through pfSense. For some reason, vhosts cannot establish connections to the outside world, although lower-layer operations ...
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Sniff tcp connection and forward to TCP connection on other adapter
I have a system with two network adapters. One of the network adapters is connected to a port mirror, so it sees all the traffic in the network. I'd like to sniff that connection for a certain TCP ...
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Traceroute/tracert fails to receive hops return information
I noticed that with some routers/gateways
when I issue a traceroute or a tracert in a 'inner' computer
the hops always fail with:
request timed out
can anybody clarify this?
what information goes ...
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Assigning IP addresses manually
I have internet connection from a local ISP at home. I see other routers and their IP addresses on my network using wireshark, when I connect the ethernet cable from ISP directly to my laptop using ...
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Attack on a Linux file server | What is the damage of this file contents?
TCP Networking
This file was uploaded using a loophole in a file uploading network program I was writing. The ability to access the server itself was too simple and the techniques I used resulted in ...
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How can I stabilize my wireless internet connection if it keeps dropping?
My current internet connection is very unstable. I'm using a Windows laptop connected to a 4G smartphone's Wi-Fi hotspot. The 4G signal is often so weak that it disconnects my phone from the network ...
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Create a TCP half open connection with bash command
Is there a way to (easily) create a TCP half-open connection using a bash command with common Linux tooling?
I want to monitor availability of a remote server using such mechanism. I know it is also ...
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Is sending a file with multiple TCP streams a good idea?
Imagine I got a large file and I want to send it through a TCP connection. The typical way is to use a stream and send continues bytes through it. But the question is, is it possible to send this file ...
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How can I know what is preventing my socket to bind to localhost:50060-50959
I am using this Python code to listen to a port on my Windows 10 system:
import socket
for port in (50059, 50060, 50959, 50960):
try:
print(socket.socket(socket.AF_INET, socket.SOCK_STREAM)....
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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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What does it mean when a portscan shows a port as "tcpwrapped"?
Interesting ports on 192.168.1.76:
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 5.2 (protocol 2.0)
62078/tcp open tcpwrapped
I see tcpwrapper ...
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How do I capture packets between a WiFi router and an internet modem?
In my home all devices were connected to my router. I want to capture all traffic so I have done below connection:
Modem --- (Ethernet to USB Adapter) --> Laptop (Windows 10) --- (Ethernet CABLE) -...
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Why does my IPTables changes not deny access from all IP addresses except CloudFlare’s ranges?
I am running apache on ubuntu 18.04. I used IPtables to deny access from all IP addressed except CloudFlare’s ranges and when I run iptables -L –line-number I get
1 ACCEPT tcp – 131.0.72.0/22 anywhere ...
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three way handshake in application protocols?
I was reading an article (https://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml) which says:
FTP, Telnet, HTTP, HTTPS, SMTP, POP3, IMAP, SSH and any other protocol that rides over ...
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SSH fails to connect from one computer but works from other computers
Problem
I have an external VPS server running Ubuntu 18.04 with openssh-server 7.6p1. I can connect via ssh to this server from many different networks except from one particular client. This ...
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How do I kill a process that is dead but listening?
I'm developing an app that listens on port 3000. Apparently there's an instance of it still listening to the port because whenever I start it, it can't create a listener (C#, TcpListener, but that's ...
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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 ?
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PC suddenly cannot do layer 3 communications any more
A PC running Win7x64 always functioned properly until a power off yesterday. From then on, the IP layer of its 3 network interfaces (2 LAN, 1 WL) only partially function any more.
A backup was taken ...
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network connection works only once
I have setup a home server and did port forwarding for http/ssh/tcp etc on the router. It was working well until very recently. My problem is that now connections seem to work only once from outside ...
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buffer deadlock prevented error from RTSP streaming over UDP
I have an issue to view RTSP streaming over UDP in the open VPN connection.
Our project is to integrate 360 degree IP camera in unity system. And we want to get the UDP streaming rather than TCP to ...
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have tcpdump show the 'conversation' as i would get from wireshark?
Is it possible to get the same output i would get from:
tcpdump port 80 -w log.pcap
wireshark log.pcap
in wireshark Analyze > Follow TCP Stream and then in the bottom drop down Entire ...
CommunityBot
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Packet reaches OS but not the process
Sorry if my issue is a bit hard to summarize in the title. That is the best I could come up with.
TL;DR Version: How do I debug when packets reach OS, but not the destination process?
Explanation: I ...
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How to enable ECN marking in IP header in Linux?
Is the ECN marking in the IP header is performed by default in Ubuntu (4.15.x kernel) or should the kernel be recompiled with a special option? I configured a RED ingress queue at an Ubuntu machine, ...
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tshark: using frame contains and write to file
i want to filter out TCP packets that contain a specific string in the frame data (data.data)
tshark -i 1 -f "tcp port 8800" -Y "frame contains FILE" -w "data.txt"
This is exactly what i want.
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Utility to display received TCP data
I'm writing code that consumes a TCP protocol - no authentication you just connect and wait for data.
I'd like to display & save this data nicely formatted - e.g. hex - and before I waste time ...
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Track down processes that connect through tcp (on certain ports) using auditd (in GNU/Linux)
I'd like to track down processes that tries to connect to a certain port (on remote host).
So, I discovered that auditd is very powerful for these kind of tasks. The following command instruct auditd ...
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When connecting via SSH, does the Diffie-Hellman key exchange take place over an unencrypted TCP session or does encryption occur before the exchange?
I'm a cybersecurity student and I'm eager to understand the basic processes of an SSH session. I wrote down the stages to the best of my ability, but need help understanding what happens right after ...
CommunityBot
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TCP RST when connecting via telnet to the application - Windows
I have an application running on Windows.
The application listens on port 54000.
I can connect to the application from the local machine and it works fine:
telnet 127.0.0.1 54000
Now, I am trying to ...
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