Questions tagged [tcpip]

Transmission Control Protocol (TCP) and Internet Protocol (IP) provide end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination.

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TCP Reno over loopback linux

When I increase delay to 2000ms and loss to 3%. I received corrupted file on server(1MB file is sent from Client to server over TCP Reno). Why could be possible reason for this? And when I send small ...
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Too many Out-Of-Order and Retransmission TCP packets showing in WireShark capture

I captured packets of a session when trying to access an ESXi login page which is across a different network in a lab environment. The issue is the ESXi login page takes too long to load, nearly 2 ...
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102 views

MAC address in TCP Header - HTTP Request?

In the same below, why are there MAC addresses in the respected request packets? Why and how did the client obtain the destination MAC address? At first I thought it was the router, but can this ...
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169 views

How to resolve VLAN tagging issues with Google Nest WiFi router

I am a software engineer and have some training and experience with TCP/IP networks, but not enough to figure out this intractable issue that appears to be caused by my choice of router colliding with ...
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98 views

Scenario where DHCP static lease AND static IP (both with same IP) on same machine?

OK the obvious answer is that "this is stupid", but please read the scenario. Let say, we have a very sensitive piece of equipment (like an alarm system), that we want to eliminate as many ...
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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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4answers
84 views

What is a (sub)network in the context of TCP/IP stack?

In the context of TCP/IP stack (that is the Internet), is a (sub)network defined as IP address + mask? If not, then how is a (sub)network defined? Clarificaltion: Given a complex interconnection of ...
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68 views

How to connect to HW device on IP address ending with .255?

I have HW device with web settings interface (similar principle like router, but it isn't router) and I changed the IP address of the device to .255. I know it is an broadcast address now and I'm ...
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Anyone know how to configure an APC UPS network management card when you don't know the IP address?

I bought a refurbished rack mount APC UPS and a network management card for a home lab setup. Thought the setup would be pretty straightforward but it's turned out to be a huge headache. First of all, ...
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124 views

When will the router remove an entry from its NAT table?

When will the router remove an entry from its NAT (net address translation) table? Most routers used in our homes maintain a NAT table to translate the public IP and port to the private ones. This is ...
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183 views

How to diagnose issue with browsing websites?

I've had an issue with my PC which started yesterday. After reboot it works fine for about 10 minutes, then i'm unable to browse any websites from Firefox, Chrome or Edge. Rebooting again fixes it for ...
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143 views

Connect adb wifi without using tcpip android

I am using nokia 5.1 plus amd my computer is Dell lattitude E6430 ETG model I'm using adb wifi and running it through cmd to run my application in mobile without using cable. I'm doing all these ...
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675 views

Windows 10 Data Usage Not Showing Up Properly

When I try to check my data usage in Windows 10 (ms-settings:datausage) my data usage doesn't show up. On the main screen it says 0MB. When I click "View usage by app" to get more detailed information ...
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124 views

Tool to send TCP RST flag

Since yesterday, we have strange traffic to our server that is causing it to consume up all memory over time. This is the pattern: time (sec) info ...
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How do Flow Control and Congestion control work together?

I am trying to learn about Flow Control and Congestion Control in TCP. So far I understand that flow control uses the sliding window method and the receiver advertises a receive window based on how ...
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How is network congestion detected in TCP?

I am trying to learn about Congestion Control in TCP and in this video (at 1:56), he says if there is no ack received, it assumes network congestion and cuts back the cwnd, no where he mentions about ...
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How to disable Path MTU Discovery on Windows 10

How can I disable Path MTU Discovery on Windows 10? Following these instructions for an older Windows version, I tried adding the EnablePMTUDiscovery registry value to HKEY_LOCAL_MACHINE\SYSTEM\...
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Is an open port on Router a threat if it's forwarded to a host which not exist

Consider we have port 65434 open on router (open for WAN). The port forwarding is done to a host which does not exist. Can a hacker exploit this open port on router which leads nowhere?
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Will the MS Windows RDP connection be a security threat if

I have read a lot regarding this subject, but still not much is clear. So the question is: will it be dangerous to use RDP for connections outside LAN if?: I have a special module which have ...
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339 views

How does port triggering know what ports to open?

Port Forwarding as I understand it When creating a port forwarding rule, the router keeps the specified external port open at all times, and simply forwards all inbound traffic for that port to the ...
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47 views

What is corel doing on my udp connections for Chrome?

I have a weird mc.corel.com address lingering in Chrome and some parts of svchost processes, what is going on?
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3answers
61 views

How these two TCP and IP work together?

I am not able to understand TCP/IP model where in layer 4 it says suppose using TCP means connection is oriented and packets will follow certain path but in layer 3 it says IP is connectionless and ...
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58 views

UDP between A and B only works if B sends packet first

I have two separate linux computers, A and B, that need to communicate via UDP on port 3000. They are each behind a different router, and I have port forwarding rules set up on each router. For some ...
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3answers
261 views

What if I spoof the MAC Address of a public device (such as a router)?

MAC addreess should be unique in a particular network. Manufacturers try to keep this unique, but there is no guarantee. Even we can create a virtual device using software. My question is, what will ...
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183 views

Router admin page not reachable through WAN port

Let us say , I have a home router which have LAN port : 192.168.0.1 WAN port : 10.137.141.195 Now , When I do 192.1768.0.1:80 , I am able to open the admin page but when I do 10.137.141.195:80 , I ...
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What does it mean to have a subnet mask /32?

I see in this question, the routing table has: 192.168.1.1/32 link#4 UCS 2 0 en0 openwrt.lan 46:94:fc:63:fc:7 UHLWIir 11 3610 en0 1200 ...
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281 views

Why is the local address the same as the peer one?

A weird issue occurred while I was troubleshooting with ss, the local address is exactly same as the peer one. Same IP address is ok, but how to explain the same port?
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Client cannot receive server Retransmission on a Windows 7 client and Windows 7 server setup

I have a Windows 7 server and a Windows 7 client application where the client application sends a query to the server application and the server application would respond. An issue can occur if the ...
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270 views

No-IP (Public IP) is painfully slow compared to direct IP address access

So I was making a software that sends screen image continuously using VB.NET (TCP) and when I type in my local IP address it sends screen image really fast but when I changed it into my public IP ...
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39 views

Connection failed error for client connected to server over wifi (TCP socket program in c)

Requirement : Need to send and receive message from two devices connected over wifi using TCP socket programming in c. Receiving connection failed for client socket. I am able to connect same client ...
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608 views

What's the fastest way to open TCP/IPv4 Properties? in Windows 10

Is there a shortcut to open TCP/IPv4 properties directly I go this way ⊞ win+R ncpa.cpl Click Ethernet Properties Scroll down to TCP/IPv4 and click it Too many steps Assume it's for a PC with a ...
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283 views

Multiple connections on same port using netconn

Trying to develop a MODBUS Slave application via STM32H743BI using LwIP 2.0.3 and FreeRTOS 9.0.0 My app should be able to handle multiple clients simultaneously. I want to create seperate threads for ...
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81 views

Is it possible to use FTP without filesystem in client?

Is it possible to use FTP protocol (not TFTP) to get file from ftp server to ftp client without using filesystem in client ? EDIT: The motives behind the question: I know that tftp can do it, but ...
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2k views

Unable to connect Android ADB over TCP/IP

I tried to connect to my phone through WiFi using Android ADB, but I can't connect it. I tried this steps: adb kill-server adb tcpip 5555 adb connect 192.168.1.16:5555 And got this message: ...
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112 views

What's wrong with this outbound iptables firewall?

I have a mail server which I'd like to secure by only allowing OUTBOUND connections on the various ports it uses. The inbound rules are working fine - they are handled by the VM host. I've not been ...
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2answers
39 views

Are errors and drops a normal thing?

My Router ( D-Link DSL 6850U ) has a status window for the LAN which shows the following: This is in contrast to the WAN statistics which show zero drops and errors. I wanted to know: 1) Does having ...
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60 views

Why does an unblocked TCP/IP port appear to be listening from one server but not from another?

I have Oracle VirtualBox on my Windows 10 machine (we'll call "hoster"). I have two linux VMs which are getting the same IP address (despite my efforts to give them different IP addresses). I tried ...
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41 views

Exploring TCP/IP Communications

According to the Lab, "The ping fails because the IP address assigned to the switch is not on the same subnet as the IP address assigned to the workstation. Even though they are on the same network ...
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1k views

Windows 7 NTLM not authenticating properly with Ubuntu 18.04

I've spent most of my day today trying to figure this out... Not exactly what I had in mind for today... but I couldn't help myself... So, here's the problem: My Windows 7 machine won't authenticate (...
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169 views

What if 2 session layers generate the same source port?

Is it possible for an application's session layer function to produce a source port which is already being used by another application for a current TCP connection? How are these kept unique? The only ...
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Why “Connection-specific DNS Suffix” is only (default) available for wired connection, not for wireless

I understand what and how to set "Connection-specific DNS suffix", and I mostly understand the purpose. My question is just about why only certain network connection/adapter has it by default (even ...
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Export Chrome Net-Internals Events

Are there any options for exporting data captured within Chrome's net-internals tool (chrome://net-internals/)? The only data that I care about are get requests for JavaScript files from a specific ...
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1answer
329 views

Wifi-Lan Port blocking

I'm writing a paired (windows) server and (android) client application suite that uses TCP connections over wifi on a funny port number. The Server advertises its availability using Bonjour/Zeroconf. ...
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1answer
852 views

OpenWRT noack and mcs rate

Are different MCS rates supported when you are running in noack mode? Context: I am using ath9k modems+Compex WPQ864 (linux-ipq864) boards. I have configured one of the boards as Access point and ...
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1answer
2k views

Practical (vs theoretical) max limit of TCP packet size

I'm a web developer who is pretty new to the industry. I was presented with a coding challenge for a job interview where I need to design a messaging system and architect a system for how it deals ...
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1answer
999 views

How can Ping not use a transport protocol?

I just learned that Ping uses ICMP directly, i.e. it bypasses the transport layer. How is that possible? Shouldn't an application (L5) use UDP or TCP in the transport layer (L4)? The way I know it is ...
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335 views

What is the reassembly path of a HTTP response?

I am trying to understand how operating systems generally implement reassembly of network requests. From my best understanding the following is true: A HTTP request is made at the application layer ...
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4k views

How to make `nc` listen on a port without setting `SO_REUSEPORT`

I want to have a nc command listen on a TCP port so I did: nc -lv 8888 Then in another console I checked if another program trying to listen on the same port would get an Address already in use type ...
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Double NAT MTU setting for the inner network

I have a home network with two routers, one behind another. The outer router's WAN port is a VDSL2 PPPoE connection with a live IP address and the MTU size of 1492. The inner router's WAN port is ...
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820 views

tcp session - http request [ x out of y] in wireshark capture

As below, i am seeing this [HTTP request 1/2] and [HTTP request 2/2] in 2 separate payload, are they separate GET request in a single tcp session or are they the same GET request ??? ==== Added full ...

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