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Hello currently im using UDP Messages to communicate my program (Made with Delphi Using IdUDPClient and IdUDPServer) on diferent computers in LAN, but yesterday i had a strange issue, one of the computers was unable to receive messages neither could other computers read his messages, All of the programs use the same UDP Port.
The only solution that worked was Restarting the router, but maybe there is an explication on why that happened?
Thank you.
I guess thats just how UDP works :) Quote from wikipedia:
UDP uses a simple transmission model with a minimum of protocol mechanism. It has no handshaking dialogues, and thus exposes any unreliability of the underlying network protocol to the user's program. As this is normally IP over unreliable media, there is no guarantee of delivery, ordering or duplicate protection.
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How can I use a broker of MQTT like mosquitto, for example, without internet?
I've downloaded mosquitto, but I really don't know how to use it in my code.
I'm programming in python, so an answer in python is better for me to understand and use in my project.
We can't really answer your question without knowing what you intend to actually do with MQTT.
What I will say is the following:
A MQTT broker doesn't require "The Internet". They will (normally) require a TCP/IP network, but this can be as simple as just a TCP/IP stack on a single machine.
The broker runs on it's own, you do not (again usually) embed the broker into your application, it is used so multiple applications can pass messages to each other.
For working with any MQTT broker in Python there is the Paho Python library. It's documentation includes examples to get you started.
I suggest you start the broker and then write a couple of test Python applications (one to subscribe to a topic and one to publish to that topic) to get a feel for how things work and if you get stuck you can ask a new question about a specific problem (explaining what you tried, what you expected it to do and how it didn't work).
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Is it possible to determine network type from iOS application ? How to determine that app is using IPv6 or IPv4 network?
There are ways in which you could test that, but it's a bad ideas in general. Trying to determine the network setup usually means that you're making assumptions, and with all the possibilities in the way networks are configured you're going to get it wrong. Networks can be IPv4-only, IPv6-only, dual stack, IPv6-only with NAT64/DNS64 etc.
The recommended way is to use hostnames with DNS and just connect to whatever you get back. That way your application will not be dependent on any specific technology and just work. If there is no network you'll notice.
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I want to use the port 12345 for hosting a server for an application I have, however the port is already in use by another program.
I have already tried:
netstat -anb
However, none of the programs listed use this port. Doing some research online I found out that Trend Micro Security uses this port. though I used to have this Anti-Virus software installed on my computer, I have long ago switched to Norton, and am still not able to use this port.
I use netgear, and have no problems using other ports.
Any help will be appreciated.
Mona.
NetGear has been known to have problems with port 12345. Try calling their support.
Belkin and Dlink work fine. So if possible, try changing your router to see if the problem goes away. If yes, then it is a router issue. If not, then contact your ISP since they block 12345 as well.
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Does anybody know how can I find out what's the interface a packet arrived on? I captured packets with tcpdump using "-i any" and now I want to find out on what interface a certain packet was received.
And another question, can I start tcpdump on an interface that does not exist yet? The code I am testing creates an interface and starts sending packets imediately. The problem is that by the time I get to hit tcpdump, some packets are already sent.
Thanks!
I think we cannot do that on a interface which is not in network .. we can work on packets which flies in the network so the Ethernet should be in network
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I am using wireshark on windows to capture my traffic.
Is there a way to capture the traffic of other computers which are connected to the same LAN.
If it is not possible with wireshark, is there other tool capable of doing this.
If you are connected to the other computers by a network hub, then you will be able to see the other computers' traffic. However, if you are connected through a network switch (which is more likely), then you will not be able to see any of their traffic.
There may be other more intrusive tools to use, possibly some that use arp-spoofing, but I would not recommend this unless you are on your own private network and know what you are doing.