I have two NICs in my Windows PC, one for Internet and the other for outbound UDP streams. Both NICs have gateways and I tweak the metrics so that Internet bound traffic goes to the first. I would rather disable the gateway on the second NIC and specify the gateway when I create the UDP socket. Is this possible? Can I force the destination MAC address on a socket?
You have to bind() the socket to the local IP address of the NIC you want to use. If you don't know the IP, use GetAdaptersInfo() or GetAdaptersAddresses() to enumerate the NICs until you find the one you want, and then you will know its current IP to bind to.
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I see this sort of address used in a bunch of examples. What does it mean exactly? Does it mean it will connect to any/all machines on the subnet that have something listening to that port? Or something else entirely? I see such usage in the docs and in books without explanation. Sort of annoying.
It is explained in the manual.
ZeroMQ supports multiple transports. tcp means you are using the TCP transport.
The address (or endpoint) for the TCP transport has the following format:
tcp://interface:port
When you bind to a local address, interface is either the IP address of a specific interface (network) or *, which means to listen on all interfaces (networks). port is the TCP port or * for a random port.
When you connect to a remote endpoint, interface is the hostname or IP address of the remote machine. port is the TCP port of the remote endpoint.
To add to rveerd's answer, what's often missed is that you can multiply bind a socket. So, tcp://*:5555 specifies port 5555 on any interface and you can bind the socket accordindly. But by calling zmq_bind() again you can bind the same socket to, say, ipc:///tmp/feeds/0, which means it will also accept connections on the /tmp/feeds/0 IPC pipe.
This is a pretty spectacularly useful feature in my view, because you can trvially have other actors local and remote to the machine though a single zmq socket.
Good day
Do you have any idea how to find WIFI routers or devices which is connected to specific LAN sockets in network?
I am try find this devices from logs Elasticsearch + Kibana namely
https://www.elastic.co/guide/en/beats/packetbeat/current/configuration-interfaces.html
With this solution I have problem with set up : packetsbeats.
Other solution which I found is : WireShark or Advanced IP Scanner or Angry IP.
With this solution /tools is problem with default setting of routers / devices which is lock ports. Its mean I can get all IPs or MACs in network but how I will get know which is IPs or MACs belonging to Routers / NTB / Mobiles ect..?
From this reason I decide find routers in network from logs by Kibana.
Do have any idea or did you make something like me?
Thanks
Wi-Fi (IEEE 802.11) is a layer-1/2 protocol, but routing is a layer-3 function, so there really is no such thing as a Wi-Fi router. There are some routers that have Wi-Fi interfaces, but they are routing a layer-3 protocol, e.g. IPv4, not Wi-Fi. Ports are layer-4 addresses for some layer-4 protocols, e.g. UDP, and they have nothing to do with routing layer-3 packets.
A router is simply a host on a layer-2 LAN. The configured gateway for your host is usually a router. The gateway is the host on a LAN to which your host sends packets destined to a different network.
Determining which hosts on a LAN are routers is a problem because you have no way to know which hosts are actually routers. You can have multiple routers on a LAN, but your host will be configured with one as its default gateway.
If you want to determine which host is the gateway for your host, then you should look at the configuration of your host, not at any particular host on the LAN.
When starting H2 tcp server and the host pc has multiple IP address's how can I define the IP that the server is going to bind to listen for connections ?
We can define the tcp port but there does not seems to be a way to define the ip address.
Thank you, Oscar
http://www.h2database.com/html/advanced.html#server_bind_address
Usually server sockets accept connections on any/all local addresses.
This may be a problem on multi-homed hosts. To bind only to one
address, use the system property h2.bindAddress. This setting is used
for both regular server sockets and for SSL server sockets. IPv4 and
IPv6 address formats are supported.
Is there a way to find out the IP address of a device that is directly connected to a specific ethernet interface? I.e. given one host, one wired ethernet connection and one second host connected to this wired connection, which layer or protocol below IP could be used to find this out.
I would also be comfortable with a Windows-only solution using some Windows-API function or callback.
(I know that the real way to do this would probably via DHCP, but this is about discovering a legacy device.)
Mmh ... there are many ways.
I answer another network discovery question, and I write a little getting started.
Some tcpip stacks reply to icmp broadcasts.
So you can try a PING to your network broadcast address.
For example, you have ip 192.168.1.1 and subnet 255.255.255.0
ping 192.168.1.255
stop the ping after 5 seconds
watch the devices replies : arp -a
Note : on step 3. you get the lists of the MAC-to-IP cached entries, so there are also the hosts in your subnet you exchange data to in the last minutes, even if they don't reply to icmp_get.
Note (2) : now I am on linux. I am not sure, but it can be windows doesn't reply to icm_get via broadcast.
Is it the only one device attached to your pc ?
Is it a router or another simple pc ?
To use DHCP, you'd have to run a DHCP server on the primary and a client on the secondary; the primary could then query the server to find out what address it handed out. Probably overkill.
I can't help you with Windows directly. On Unix, the "arp" command will tell you what IP addresses are known to be attached to the local ethernet segment. Windows will have this same information (since it's a core part of the IP/Ethernet interface) but I don't know how you get at it.
Of course, the networking stack will only know about the other host if it has previously seen traffic from it. You may have to first send a broadcast packet on the interface to elicit some sort of response and thus populate the local ARP table.
Windows 7 has the arp command within it.
arp -a should show you the static and dynamic type interfaces connected to your system.
Your Best Approach is to install Wireshark, reboot the device wait for the TCP/UDP stream , broadcasts will announce the IP address for both Ethernet ports
This is especially useful when the device connected does not have DHCP Client enabled, then you can go from there.
You can also get information from directly connected networking devices, such as network switches with LDWin, a portable and free Windows program published on github:
http://www.sysadmit.com/2016/11/windows-como-saber-la-ip-del-switch-al-que-estoy-conectado.html
LDWin supports the following methods of link discovery: CDP (Cisco Discovery Protocol) and LLDP (Link Layer Discovery Protocol).
You can obtain the model, management IP, VLAN identifier, Port identifier, firmware version, etc.
I am developing an P2P application where a peers talk to the server to inform its Private and Public IP. The application uses UDP for communication.
To get the private IP the client uses gethostbyname and bind it to that IP. The problem is when the system has more than one NIC. The problem is when one of the NIC is not connected to internet. So to avoid it i am using INADDR_ANY and bind it.
Now i need to get my local IP address to inform to the server. Is there any API which will tell me which IP address of the NIC is active?
You need to bind to an explicit IP address rather than INADDR_ANY as binding to INADDR_ANY will mean that calling getsockname() on the socket to get the local address will simply return INADDR_ANY.
So, what you need to do is iterate the available endpoints (using getaddrinfo()) and create a socket on each. These will then give you the correct address if you call getsockname() on them later.