I'm trying to write a function that can get me the IP adress (and the name of the device as bonus) of devices that are in my network, the network is gonna be a direct connection between two computers using Ethernet cable or creating an access point (using wi-fi)
I tried to search about how to do it but it seems like I need to listen to the network or something which seems to be difficult.
hope you can guide me to what I should do or read to get started.
Note: I'm using Windows on both computers.
Edited:
P.S: I need the IP Address so I can send a message to the other computer using winsock in a Client/Server program I wrote.
can't I make the server send its IP to the client or the opposite ?
If your software is running on both machines, you can have one (or both) machines send out a particular broadcast (or, if you prefer, multicast) UDP packet on a specific port. Your program should also be listening on that same port. When it receives that packet (using recvfrom()), recvfrom()'s fifth argument will contain the IP address of the machine that sent the packet, i.e. the IP address you want.
(If OTOH your software is not running on the remote machine, you'll need to use some more general-purpose discovery mechanism such as mDNS or LLDP -- hopefully you won't have to do that, though, as it's a good deal more complicated)
Related
Scope:
OS: MACOS, Windows;
Language: C++Boost library;
Description:
LAN has N computers with MacOS and Windows operating systems, where N ≈ 10. The IP addresses of the computer are not static and assigned by the network. On one of these computers (machine S) a socket server application is running. And on another machine (machine C) a client socket application is running. This is not a static setup, and next time it might be different computers with different IP addresses.
Update:
a server machine -- is a slave. A client machine is a master. A user can install client software in any computer in LAN, and server software in any other computer in LAN. Server take responsibility for the calculations which takes a lot of resources and just send a result to a client. So, the main idea is: a user of a master computer should not provide a server IP address, but the client soft should be able to discover it by itself.
Task: Client socket application does not know Server application IP address, and should be able to discover it.
Solution should be a cross-platform one (Boost C++)
Please suggest the best practices.
My best guess was: retrieve all the IP addresses of connected devices and socket->send_async_to them. And if I get answer in handle_receive callback -- this is a server app. But I did not find a way how to get all the IP addresses of LAN devices.
Thank you in advance for your suggestions and ideas.
use UDP to send request to all the computers in the network.Write a thread in server to respond udp request. then you can get response from the server and get the socket ip.
First, I want to give thanks for that amazing lib! I love it. A client is connecting himself to a server. The server should save the IP and do stuff with it later on (I really need the IP). I found that answer: http://lists.zeromq.org/pipermail/zeromq-dev/2010-September/006381.html but I don't understand how I get the IP out of the message (a XREP)... I think I am only able to read the ID, but the IP is managed internally by 0MQ. His second solution suggests to send the IP as part of the message, but I don't understand how to get the "public"-IP. I found that post: Get TCP address information in ZeroMQ
is pass bind a service to an ephemeral port, get a full connection endpoint ("tcp://ipaddress:port")
I don't get how this works. Does he mean something like a web-service?
In my opinion, it would be best to get the IP out of 0MQ (it has the IP already). I would even adjust 0MQ for that, if somebody could point to the place where the IP is saved, couldn't find it. The socket types are not that important, at the moment. I would prefer smth REQ-REP like. Thank you!
Summary:
TL;DR answer to your question is: you can't get IP address of the peer that sent a message, using ZeroMQ API.
Explanation:
ZeroMQ does not expose peer IP address because it is irrelevant for the message based communication that ZeroMQ is designed for. When it is possible for ZeroMQ to get IP address of client that is connecting to server (in example using method described here), it is useless. For a longer explanation here is how it works inside ZeroMQ and any other server implementation.
Server side of the connection does not handle connected clients by the means of the hashtable that maps IP to client, but by keeping track of connected "sockets" (socket descriptors) - when a server accepts (using accept()) a connection, it receives from operating system socket descriptor to use to communicate with connected peer. All server has to do is keep that descriptor around to read() from and write() to that client. Another client that connects to server receives another socket descriptor.
To summarize: even if ZeroMQ would be able to provide you with IP of connected peer, you should not depend on it. ZeroMQ hides from you connection management so you can focus on messaging. Connection management includes reconnections, which may result in a change of IP without changing the actual ZeroMQ socket connected on the other side.
So here's an example of why you might want to get the ip address a message was delivered from: we have a server whose job it is to synchronize updates onto occasionally-connected clients (think mobile devices here, though this is an extreme example of a mobile deivce.)
When the mobile unit comes onto the network, it sends a list of it's firmware files to the server via a dealer-router connection. The server has a list of all applicable firmware files; if the client needs an update it will initiate an update via a separate mechanism.
Since the IPs for the devices can (and do) change, we need to know the IP address associated with the mobile device FOR THIS CONNECTION, i.e. right now.
Yes, we absolutely can have the client send it's IP address in the message, but that's a waste of another n bytes of valuable satellite air time, and while not pure evil, is sure annoying. Zmq already has this information, if it didn't have it, it wouldn't be able to generate replies. The address is in the socket data, there's no reason the message couldn't (optionally, for all you guys who use wired networks and think disconnects are the exception) include a reference to the socket structure so you can get the address out of it. Other than pedantic religiosity, which is far too common in zmq.
The way ZeroMQ is designed there's no information provided on the remote IP. As far as I know you have to manage this through your application by sending that information as a message of some sort.
The messages themselves use an IP-agnostic ID which has more to do with the instance of ZeroMQ running than any particular interface. This is because there may be more than one transport method and interface connecting the two instances.
I am having troubling using the new bind feature of the QTcpSocket class in Qt5. Any help figuring this out would be appreciated.
I have a multihomed server that contains two NICs each with a separate IP address. I have setup routing on the servers so that sending from the source address is sent out of the appropriate NIC regardless of the target remote address. That is, sending from x.x.x.0 goes out over eth0 and x.x.x.1 goes out over eth1 regardless of who the data is being sent to. These NICs are connected via ethernet to long range Wifi links that are then connected to a switch. These wifi links act as a transparent bridge and can rather be seen as two ethernet cables (but they are limited in bandwidth). The switch is then connected to a computer. The goal is to transfer data between the server and the computer, and to use the two wifi links in parallel to increase bandwidth. Although the server is physically a server, the software has the computer running as the software server (as others connect to it). That is, the physical server (software client) opens TCP sockets and attempts to connect to the listening computer (software server).
I use the bind feature of Qt5 to bind one TCP socket to the eth0 IP address and bind another TCP socket to the eth1 IP address. I have verified this works with other programs like PING or file transfer via SCP. See http://qt-project.org/doc/qt-5.0/qtnetwork/qabstractsocket.html#bind
When I call bind the call succeeds and subsequent requests for the local IP address returns the correct value. E.g. socket->bind(ip) returns true and then socket->localAddress() equals ip. However, when I call connectToHost the localAddress is lost when it starts the connection attempt and after connecting it has a different localAddress that is not the one I wanted it to have.
Can anyone shed light into what is going on? I am trying to avoid rewriting the software to reverse the roles of software client / server as these programs are quite big. Thanks for the help.
There is an open bug on this in the Qt project bug tracker.
I would like to time how quickly the latency is of a system by sending a packet with the same dest IP as the source IP. Is this relatively simple to do?
How would you custom-build the packets?
Would setting the two IP addresses achieve what I am after?
What is the best timing method?
Any tips/ideas at a low/high level would be greatly appreciated. I intend to use C/C++ on Unix with the boost libraries and libpcap.
EDIT: I should add I will be doing this on a home network, behind a router. I presume the packet will go to the router and come straight back if I were to use 192.168.2.1 (local IP of my system) for the source and dest addresses.
You can just try ping to your own IP. this will produce ICMP packets. There are libraries which also allows you to do the same from an application.
If you want to create packets for yourself you can use socket API. Remember, you can send the source IP address and destination IP address as same, but the port number needs to be different.
For timing you need can use gettimeofday function.
EDIT:
you can ping from your C++ program. See: http://verplant.org/liboping/ or check out some other forum. The reason i emphasized on ping is because it returns right back from the network stack. If you send a UDP packet on the other hand, expecting the application to return and echo, then the processing time of the packet on the listening server gets added.
If you ping to local machine ip (or even lo) it returns without going to switch or next hop router. It will respond even if you remove your eth cable or wifi.
What you are trying to do is implemented in NTP daemon with NTP protocol though.
You don't need a custom package for this. Just create a socket connecting to the same ip-address as the server, and start sending packages. Note that these packages will never leave the network stack, so what you will be measuring is basically how quick the system copies data between user-space and kernel-space.
For the timing, you can use the clock function, it's probably the one most widely used for such things.
I have a network of computers that they will connect to the a server with DHCP, so I don't know what Ip address a computer will get when I connects to the server. If 192.168.0.39 for example is connected to the server can I identify the real computer behinde this ip address? ( I can install an external application on each client in order to send some data to server for example mac address or so... )
If you are responsible for the DHCP server, you can configure it to hand out a specific IP to a specific MAC. Having done that, you can be reasonably confident of that mapping -- it is possible to spoof MACs, so if you are worried about security, you'll need a much more heavy duty approach. If this is a casual application where the risk of that is low, you configure your DHCP server to hand out IPs based on MACs and then make use of those mappings in your application.
You might not even need the IP address. On an Ethernet network, all communication from a computer, whether it's IPv4, IPv6, or even IPX will be labelled with a MAC address that's stable over time and unique per network card.