On linux platform, I want to have dhcp client.
port any open source client to my app (which seems to be a bit time consuming)?
or communicate with the standalone client app via Signals?
or anyone knows any dhcp client library?
thanks for any advice.
You mean you want your app to tell the computer to DHCP? I would talk to dhcpcd using command line arguments and not do tons of extra work.
Related
I am working on a project and I need all my ESP32s to communicate with my PC to relay information. I am developing my MQTT server and I would need a way to find the IP of the PC which hosts the MQTT server to be able to send it the data from the ESP32.
Long time ago I tried to deal with NetBIOS broadcast but it's really unstable and complex to code in Arduino C++.
mDNS is what you are looking for.
The correct service type for MQTT is _mqtt._tcp.
There are plenty of libraries that support publishing mDNS services such as Avahi on Linux.
Windows doesn't support mDNS as a client but iirc you can install the Apple printer driver kit to add support.
If you can't get mDNS to work, and if you have full control of the LAN's router: some routers can act both as a DNS proxy and as a LAN DNS server, see here for example.
You can then connect by name or get the IP address without further configuration of the ESP32 (unless you change the server name, of course). It won't show you directly if the _mqtt._tcp service is available, though.
I have two applications. One is the server app and the other is the client app. The server app listens for connections and then feeds messages to all connected clients.
So far all my testing has been done by running both applications on the same machine, and this is working fine. Now though I am trying to test the server running on one machine and the client running on a different machine.
Each of these machines are within my own home network. That network is behind a router with a firewall. From what I have read, my problem might have to do with port forwarding not setup on my router. Does that sound likely?
Is this something I can fix with just my code? Do I really have to require all my users to manually open the port on their firewalls? I have used plenty of other commercial applications that connect to servers and don't require me to open ports on my firewall. What is different about those applications and mine?
Then again, maybe I am barking up the wrong tree here. Maybe there is some other problem preventing my code from working in this situation?
I can provide any code snippets that might help, but I am unsure as to where to start looking and I don't want to just post my entire solution :)
Thank you in advance
You need to bind to 0.0.0.0 (simplified version) in order to accept connections not coming from the local machine. Have you checked that you don't bind to 127.0.0.1?
When you bind to 0.0.0.0 you actually bind to all current and future addresses of the current host and so will be able to accept connections from everywhere, you can also bind to just the address of one of the network interfaces.
I'm able to access a telnet server via PuTTY which opens a terminal and allows me to send commands to retrieve data/logs and start/stop processes. I'd like to begin some research into how to access this server via C++ in order to automate the connection and the commands for testing. Basically I need a telnet client that can connect and authenticate itself, and write and read to/from the server as if I'm typing in a terminal. Where should I start my research? I've tried a couple examples including:
http://lists.boost.org/boost-users/att-40895/telnet.cpp
When I compile and run
./telnet 192.168.1.26 23
Nothing happens, but when I connect to the server with PuTTY I get:
QNX Neutrino (localhost) (ttyp0)
login: root
password:
#
Any help would be greatly appreciated.
Notes:
- I am using a Mac running OS X Version 10.7.3 with i686-apple-darwin11-llvm-gcc-4.2
- I am allowed to be doing this.
- I use PuTTY on my Windows 7 machine, the connection is ethernet to USB ethernet adapter, and the settings for the Local Area Connection Properties > TCP/IPv4 Properties: are a specific IP address, Subnet Mask, and Default gateway, which might be useful information.
Thanks
Learn how to program TCP/IP sockets. You can use the boost libraries, or straight C style BSD sockets. Some info here, here and here. If paper is your thing, you could get Volume 1 of Unix Network Programming. That book has such a good reputation that you get votes just for mentioning it on StackOverflow.
What you want to do closely matches the functionality of telnet and expect. You can have a look at there sources here and here for ideas.
Consider just using expect to solve your problem :)
You should start by learning the network API for the system you're trying to connect from. Telnet is just sending straight up text through a tcp/ip socket.
I'm trying to implement an auto-connect feature for my Android application DroidPad, which is basically a TCP server running on an Android phone which the PC application connects to.
To make the process easier for the user, is there any way in (portable?) C++ to scan the IP addresses on the local subnet, possibly ones with a certain open port? I've tried using UDP broadcasting, but couldn't get it to work. I'm currently using the wxWidgets toolkit for GUI and libraries.
Any ideas?
I found a solution: wxServDisc. It uses mDNS (aka Zeroconf / Bonjour) to discover devices on a subnet, and is also based on wxWidgets.
I'm running a client/server application locally on my Windows XP PC and for testing purposes I want to run multiple clients.
The server has a configuration file containing the IP addresses of the clients that can connect; in the real world, these would all be on separate hosts with separate IP addresses.
Currently I am able to test locally with a single client which binds to 127.0.0.1 however because I can only have one client-IP mapping in the server configuration (that's how the system works and can't be redesigned!) I can only run one client on my development PC.
I've tried to start another client application bound to 127.0.0.2 connecting to the server which is bound to 0.0.0.0 however the server thinks that the client is connecting from 127.0.0.1 again and so rejects what it believes is a second connection from the first client.
Can anyone suggest a way to get around this problem? I believe I could run one more client bound to the external IP address of the PC but I'd really like to be able to run multiple.
I know I could use VirtualBox or similar to run new instances but I'd like all of the client applications to be running in the Visual Studio debugger.
Any help greatly appreciated!
Nick.
PS. Not sure if it matters but the applications are written in C++ using standard winsock sockets.
You might be able to create more loopback interfaces. See the chosen answer to How do you create a virtual network interface on Windows?
AFAIK Windows 7 (maybe Vista too) lets you add multiple IP addresses to a single interface (card).