I have a few 'smart' relay boards on different sites. These boards have a ethernet connection and are running a built-in web server on TCP 8080. I can access them from the local network and control them via a browser.
To control these boards remotely, I could assign them a fixed local IP address, open TCP port 8080 on my router and forward it to that address. But this is a risky thing to do, off course.
And I would have to do this on the different routers (from different IPSs) on each site and keep track of all these public IP addresses. (Via a dyndns service. Most routers are not VPN-enabled, afaik.)
Is there a better way using VPN-tunnels? I already have a Linux VPS running for other purposes and could install a Raspberry Pi on each location. All these Raspi's could connect to my VPS. And I would no longer need the dyndns.
Maybe, I could also find a way to map the URLs for the different relay boards to a more human-friendly form. Like this: http://myvps.domain.com/site2/relayboard3
How can I achieve this? I could install OpenVPN on the VPS server and the Raspberry Pi's (one for each site). But how do I have to configure this? VPS in the role as VPN server and Raspi's as VPN clients?
(I assume the gateway address from the relay boards has to change to the local address from the Raspberry.)
And do I need a VPN client om my Android phone to be able to browse to the relay boards or not?
What do I need to forward the http connections to the correct relay board? A proxy server?
I'm using Twilio to send and respond to messages. It was working normally, but since we moved to bay area the responding function doesn't work now.
So what happens is when the user send message to us(the IP address of our own computers) from their phones, our server can't receive anything. When we check our Twilio account, we know that the msg was indeed sent to the Twilio server. So we think it's the problem of linking between Twilio server and our IP address. We are suspecting that the IP address is virtual IP address here, which makes Twilio server can't find us. Is our suspection correct? if yes, what should we do? If not, what would be the possible problems?
Apologize for having a description not very clear, but it's pretty much everything of the problem. Please tell me if you need any additional information.
You probably need to use a dynamic dns service. Then you need to find what port Twilio sends the SMSs to the client(your computer), and make sure your firewall is forwarding that port to your computer. Odds are this is a firewall issue, especially since you say everything worked before you moved. Has there been a change in your network setup? You need to be aware of both hardware and software firewalls in your setup.
How is the firewall configured on your router? You need to forward requests to your router to your local IP address. Example: My local ip is 192.168.1.5 my external ip is 245.932.4.3 (This is the value you get from myipaddress.com) Thus you need to set your router (which has ip 245.932.4.3) to forward requests on port x (where x= the twilio outgoing port) to 192.168.1.5
I have a project based on windows Phone 7.5, which contains a module to ping remote devices (in the same subnet or internet). I tried to perform an echo request and reply on port 7. but reply does not comes back, rather, an NullReferenceException occurs when I try to access SocketAsyncEventArgs.Buffer. I also tried creating ICMP type packets in app, but no luck.
As far as my understanding goes, icmp packets are not allowed to perform ping. however, from desktop, the phone can be pinged if ip address of phone is known.
I have checked many applications on marketplace (like Console WP7 Lite, TestMyNet), those can perform ping by sending icmp packets and can also access Round trip time of ping operation.
I am wondering how those applications can ping to remote (accessible) devices, when windows phone sockets does not allow icmp packets.
Can anyone help me.
Thanx for help in advance
Are you sure these apps can ping local network? For example can they ping WP Wifi interface's gateway or the WP Wifi interface itself? Or can the only ping hosts on Internet? I tried both apps mentioned by you, and even more and they ping everything except local network. That is why i was convincend that they use external server to perform pings and roound-trip is only calculated or estimated somehow.
Piotr Wojtowicz
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 often run into problems where I can't get something to connect to something else. I usually forget to check something obvious. Can you help with:
A tip/technique for diagnosing a connection issue
The name of a tool or application that can help (and the situation in which it's useful)
I know the question is a little non-specific, but hopefully the answers can form a useful starting point for anybody who's stuck trying to get computers/programs talking to each other.
Please can you give one answer per answer so the best ones can be voted up.
Simple checks to run when debugging network problems:
Has each machine got an IP address, Go to command prompt and run ipconfig. Key things to check here are the interfaces and ensuring the appropriate ones have IP addresses.
Check both machines IP addresses are in the same range and subnet if you are running it on an internal or Virtual network.
Try pinging each machine from the other to see if they can communicate with each other. Note that some firewalls will block ping requests.
If Pinging fails then check to see if firewalls are active. If the communication is within a 'safe' internal network then try disabling the firewalls and re-pinging.
If the connections are over a wireless network then check signal strength.
If pinging fails and you are connecting through several networks then try running a tracert to see at which will may show you where on the network the connection is failing.
If you are able to ping but not connect then check firewall settings and network connection settings. Windows 2000+ has the capability of setting port an ip access on a connection properties.
Try drawing a network diagram of the connections to help in visualising the problem.
If you are connecting through routers, firewalls and loadbalancers then check that all devices are not tied to any specific ip addresses and that the IP address redirection (if in place) is correct. Also check any NAT logs to see if connections are being received and properly re-directed.
Wireshark
Latest versions of ProcMon
netstat
Wireshark www.wireshark.org
Wireshark is a network protocol analyzer for Unix and Windows.
Features:
Deep inspection of hundreds of protocols, with more being added all the time
Live capture and offline analysis
Standard three-pane packet browser
Multi-platform: Runs on Windows, Linux, OS X, Solaris, FreeBSD, NetBSD, and many others
Captured network data can be browsed via a GUI, or via the TTY-mode TShark utility
The most powerful display filters in the industry
Rich VoIP analysis
Read/write many different capture file formats: tcpdump (libpcap), Catapult DCT2000, Cisco Secure IDS iplog, Microsoft Network Monitor, Network General Sniffer® (compressed and uncompressed), Sniffer® Pro, and NetXray®, Network Instruments Observer, Novell LANalyzer, RADCOM WAN/LAN Analyzer, Shomiti/Finisar Surveyor, Tektronix K12xx, Visual Networks Visual UpTime, WildPackets EtherPeek/TokenPeek/AiroPeek, and many others
Capture files compressed with gzip can be decompressed on the fly
Live data can be read from Ethernet, IEEE 802.11, PPP/HDLC, ATM, Bluetooth, USB, Token Ring, Frame Relay, FDDI, and others (depending on your platfrom)
Decryption support for many protocols, including IPsec, ISAKMP, Kerberos, SNMPv3, SSL/TLS, WEP, and WPA/WPA2
Coloring rules can be applied to the packet list for quick, intuitive analysis
Output can be exported to XML, PostScript®, CSV, or plain text.
work the OSI model from the bottom up
Physical (Do you have a network adapter/connection)
Link layer (arp, ethernet port blocked by network team (I've seen this where locked down environments see two MAC addresses coming from one workstation port and shut down the port)
Network layer (ipconfig, tracert, ping,)
Do you have a network address (DHCP, fixed)
Are you on a proper subnet/have routing between subnets
Is something in the middle blocking you
firewalls, routing tables
When in doubt, check to see if the windows firewall is messing with your communications. 8 times out of 10, it's at fault.
Using tracert is a good start to see how far along the chain you are getting.
For virtual machines it's usally a good idea to make sure you have the loopback adapter set correctly in the Host os.
Most frequently used tool is the ping. It can be used both to test your connection and the availability of a target
Second tool is the tracert if you want to see where the packets get lost.
For more advanced debugging I use the following tools: nmap, wireshark, etc.
Windows has a netstat utility which is pretty similar to the Unix netstat and can do a number of different things that might help you solve network issues.
Random example:
netstat -r displays routing information
netstat /? for usage information
Since you said you're using 2 virtual machines I would hazard a guess that both machines are setup in a NAT configuration (rather than a unique network device) -- In the NAT configuration, neither machine would (typically) be able to ping the other.
If you're familiar with the command line, you can try the "netstat" command.
You can also try "arp -a" to list all the IP/MAC addresses known to your PC.
The "tracert [ip address]" command will show you how many gateways/routers your packets jump through on their way to their destination. (This is probably not helpful if both machines are on the same network, though.)
And don't forget to check your Windows firewall settings.
Otherwise, if you want to get down and dirty, you can try the packet sniffer known as Wireshark: http://www.wireshark.org/ (aka. Ethereal)
Pull the network cable out
If you can get some communications to a device (eg a ping), but can't get your program to talk to a service on the computer. Then, try pulling the network cable out and see if the ping stops. This will verify you're communicating with the computer you really think you are.
On windows i user PortQueryUI : http://www.microsoft.com/en-us/download/details.aspx?id=24009
DNS activity: Portable DNS Cache and Firewall;
General network activity: Wireshark, Network Monitor;
Windows utilities: ping, netstat, nslookup.
You need to be use the process of elimination, for example if you can ping the ip address but not the hostname then there's DNS issues. If you can ping the system but not connect to a share etc.
DNS out of sync
If you're using a virtual machine and you perform a roll-back on it, then it could become out of sync with the DNS (Domain name server). Try to remove and re-add the machine to the domain, or if you've got access to the DNS machine, then get it to flush its cache.