I'm developing small demo application for Windows Mobile 6.1 to get the list of all serial ports and the Bluetooth devices configured on them. I'm facing some weird problem.
I can see total 10 COM ports when I go to Settings->Connections->Bluetooth->COM POrts. But when I use SerialPort.GetPortNames() to get all the ports, it shows 9 ports i.e. one port less. The last port i.e. COM09 is not returned in the result set.
Then I removed one of the paired devices configured on one of the COM ports (COM08) and SerialPort.GetPortNames() returned the result set WITHOUT the COM08 port.
I further tried to know which COM ports are still unused. When i tried to create "New Outgoing Port" manually on one of the 'unused' (as per my program) port, it gives a message saying "COM port cannot be created"!
Could someone tell me the reason and guide me further to resolve the issue?
The Bluetootch driver is probably modifying the registry key where the Drivers are and GetPortNames is probably looking through that key.
Take a look at both HKLM\Drivers\BuiltIn and HKLM\Drivers\Active with the remove registry editor and see what's happening. You can likely write your own parser that looks at these values for what you are after.
Related
The RFP for TFTP says that TID's in most circumstances:
should be randomly chosen, so that the probability that the same
number is chosen twice in immediate succession is very low.
The thing is, these "TID"s are also used as UDP port numbers. But a typical network interface cannot just be dedicated for TFTP use. Some ports are liable to be in use, and others should essentially be "reserved" for specific applications. I'm not even sure where a program could go to look up this information at runtime.
So how is a TFTP implementation supposed to deal with this?
Since the host selecting the TID/port is the one opening it and telling the other party which one it's opened, you can simply try to open the port; if it's already in use or otherwise unavailable, this will fail, and you can re-try with a different port. (Note that since UDP and TCP are difference protocols, a TCP application and a UDP application can both be using the "same" port, since they are not, in fact, the same at all!) Do this in a simple loop until you find a "good" one. (Probably best to define a maximum number of tries and simply fail the connection if that's met before a good port is found, as this could be a sign of other issues that prohibit this from working at all.)
Stick to the ephemeral port range to play nice with best practices, although note that different systems define different ranges for this purpose. You could pick the range suitable to your system, or simply try to use a port above the "well-known" port range (i.e. above 1024); this may not give you an "ephemeral port" per se for your system, but so long as you can open it it should work fine.
I have a weird problem. I have a successfully working C++ (boost asio) P2P application which works on most of the NAT. The problem is when I give the initial start port number as 1000 it checks if 1000 is free else increment by one and chooses a port and starts handshaking. But when I have 10000, 20000, or any other huge port number the hole punching doesn't work on port restricted cone NAT.
How is that possible? I am pretty sure it nothing to do with the code. and recently it doesn't work on one of my friends' full cone NAT as well, but it has worked in many other full cone NATs. What could be the reason? Is there something I am missing about how a NAT behaves?
In many NAT implementations, there are protection rules in place which prevent one host from tying up a large percentage of ports on the WAN interface, e.g. like described here.
Depending on the router, the NAT table entries have different lifetimes, and there are always limits on how many ports can be allocated to a single client (I've seen numbers from 128 to 4096).
So I think when you get to the point where you need to use high ports, the NAT table for your source IP address is already full (or almost full) with entries from old connections, or connections from other apps, so the router either decides to decline or can't fit the new NAT entry for your port.
However, to be sure, I would try to repeat that on a controlled environment collecting Wireshark dumps on both sides of the NAT and analyze the packets. If possible, it would also be helpful to enable router logs and peek into them.
I understand this is not a "magic bullet", but hope it somehow helps you.
Don't try to choose the port number yourself. The operating system can do this faster and better than your code can.
Bind your socket to port 0 and let the OS choose an available port number for you. You didn't specify what programming language, but it usually involves a call to getsockname() after the bind() call is made to discover what local port is going to be used. Java and .NET have equivalent APIs for doing the same thing.
Then follow all the other steps here:
https://stackoverflow.com/a/8524609/104458
Not sure if this'll help but have you tried having one instance of the client application starting at 1001 and the other starting at 1000, then both increment by 1.
While the 1000 will fail on client B, client A has already tried 1001 and so punched that hole, so hopefully it'll work, right? In theory, it sounds OK in my head.
I know there are various programs that sniff packets like WireShark, but I'm pretty sure you can only view the data. I want to know if it's possible to edit incoming packets. I'm not sure if packets are the right term. I just want to edit incoming data that is recieved through the internet and who's destination is a specific application. Let's say I am playing an online game. As it loads my computer, it is recieving information like "This person has 10 coins in their money pouch". Obviously not exactly like that but you get the point. I would like to be able to change the data so it is say 100 instead of 10. I know something like this would be possible if you were to do this: Imagine my computer is connected to the internet with an ethernet cord. There is a device attached to the ethernet cord which recieves the data and changes it and then lets it continue to my computer. I would just like to know if this is possible, and how it could be accomplished.
Thanks!
The way I do it, is one of 2 ways:
1.
If your application supports it set up a HTTP Proxy on your machine and you could software like burp / Fiddler to mess with the data
If not (the protocol is not HTTP) you could use either one of 2 options i'v tried [Both based on Hooking the API calls from the application to the OS]:
EchoMirage software that allow messing around with the packets
[Bit more advanced: ] There is a debugger named OllyDbg which has a plugin named Universal Hooker; it enables to hook any window API function and execute a python script on demend. the uHooker contains examples for how to hook WSASend and WSARecive (which are the API functions used in windows sockets).
A Sprint cellular modem plugs into a laptop - often the PCMCIA slot. To connect, the user opens a program called the Connection Manager. This program has a menu option to display the serial number and phone number of the modem that's currently inserted.
Does that imply that the serial/phone number of the modem could be available to other programs running on the system? (Note: let's assume this is Windows XP.)
Specifically, could a company's VPN software be configured to pass along information about which modem is being used to connect?
Finally, is there existing VPN software that already does this, or would it have to be custom-programmed?
Sometimes you can get the modem's serial number using the AT command set. To see this in action, go to your control panel and open up Phone and Modem Options. Select the Modems tab, select the modem you're interested in, and choose Properties.
In the modem window, select the Diagnostics tab, and press the Query Modem button.
This opens the serial port and sends a series of AT commands to gather various settings and information. You can open the serial port in your program (or a terminal program), send the AT command, and get the same information back.
You may need to check your specific modem's AT command set to find where the serial number is stored, or use a serial port spy program to see how Sprint's program does it.
I'm not aware of any VPNs that use this information, and I can think of several ways to spoof it, since communications between the modem and the computer are not cryptographically secure.
-Adam
Open hyperterminal or make a serial port connection programatically and use Hayes AT language to talk to it. Most software also has it listed in the device properties and/or diagnostics.
AT+GSN
press enter
The company I work for makes hardware that communicates to the computer though a serial port. Third party companies write software that communicates with our hardware.
There are times when I need to diagnose our hardware. However, a third party software app connects to the serial port when Windows starts up, blocking any other connection. I don't know the name of this application/service and it's not always the same one.
Is there any way to either:
Find the name/pid of the app/service that is currently using a given serial port or
Steal the serial port connection from another app.
vb.net preferably, but I'll take a language agnostic answer as well.
You can use the process explorer tool also from SysInternals to search for open handles. In this case you would want to search for 'Serial' since it uses device names that may not map to com port numbers. (e.g. COM1 is \Device\Serial0 on my system).
If you want to take control of the serial port from another app I think you would need co-operation of the driver.
As Rob Walker said, you can find who's using a serial port using Process Explorer. Most of the time, typing Ctrl+F and searching for "serial" will show you who has a serial port open, but I just ran into a situation where my "COM3" serial port's handle appeared as "\Device\VCP0". It may be strange because it was running under VirtualBox with a USB-to-serial connector.
If searching for "serial" and "device\vcp" don't get you any results, you may be able to figure out how serial port handles are named by opening one with a known program. In Process Explorer, display the lower pane with each process's open handles by typing Ctrl+L. Click on the process that you used to open the serial port and look through the lower pane to see which handles look like they might be a serial port. You can open and close the port while you're looking, and the file handle should appear and disappear, as well as being highlighted in green or red. Of course, this is only possible if you have more than one serial port or the serial port you're trying to diagnose isn't always locked by some mystery process.
Sysinternals has a slew of utilities I find very useful and educational for tracking down what processes are doing to the system.
They have a utility that does exactly what you need called Portmon, and give some information on how it works near the bottom of the page. That info and a few well-asked questions will probably give you everything you need to implement it yourself if the utility isn't enough.
-Adam