Currently, I'm successfully running a mosquitto broker, subscribing to topics and publishing messages with clients in a local network.
How can I communicate with another local network which is located at a different IP address?
Should I set up 2 mosquitto brokers, one for each local network?
The PC in the other local network needs to be accessible from Internet, so if it is behind a firewall, you need to set a port forwarding rule inside your router. The rule needs to forward the traffic from the public IP address to the internal LAN private IP address of your broker.
Remember that MQTT uses ports 1883 and 8883 (for SSL).
Because mqtt use tcp connections, there is also a safe way to do this as follows:
A private broker A behind a firewall.
B private broker B behind another firewall.
C cloud broker C on the internet.
Setup the bridge A to C in both directions. This must be configured on A. The safe tcp link to the internet will be created by A.
Setup the bridge B to C in both directions. This must be configured on B. The safe tcp link to the internet will be created by B.
This will create a much safer bridge and can be done even if you do not have control over the router or firewall.
This all depends on how your system needs to work, but you could use multiple brokers (one in each network) then create what is known as a bridge between the brokers.
This has the benefit that the each network can continue to work independently of the others should there be a network outage.
Bridges also allow you to control which messages are shared between sites. Details of how to create a bridge are in the mosquitto.conf man page:
http://mosquitto.org/man/mosquitto-conf-5.html
But as Paolo says, you will need to set up port forwarding for port 1883/8883 on your router to expose the the brokers to the internet.
Here are the steps to allow public connections to MQTT server within private space (home)
allow port forwarding on your router
public port 1883 should be forwarded to private port 1883
IP Address to forward requests on this port should be of the IP address of MQTT server/PC in your home/private network
Update Mosquitto configuration to allow public listeners
add line listener 1883 0.0.0.0 under #listener port-number [ip address/host name]
This will allow requests from any source on 1883 port to be handled by your MQTT
Restart MQTT
I could successfully open up my MQTT server to public/internet traffic by following above steps after many trial and errors with many different configuration changes.
Related
I'm trying to build a peer-to-peer game, where each player is both a server and a client with tcp sockets. The sockets can connect fine when I'm using local ip:s, but of course fails when I'm trying to use external ip:s.
But I'm thinking that the players should be able to connect to each other if they just knew the external address + port that the router assigns to them.
Setting up port forwarding is out if the question since I don't have access to the players routers.
I'm thinking of having a server in between, just to be able to read the external address and port of the players, and tell the other player about it so that it can connect.
But I haven't found any info anywhere if that's how port forwarding works. If computer A makes a request from a local address and a port to the server, and the router assigns this address + port to an external address + port, and the server tell computer B which address + port to use. Can computer B use that external address + port to connect to the computer A and start a tcp socket with it? Is there any way to know that this external address + port stays the same when another computer makes a request against them?
The problem is that most people don't expose their PC directly to the internet. They have a router that has an external address. When you send a packet to their IP address, it is going to their router. The router doesn't know where to forward it to and what port to use without port forwarding.
So, getting everyone to enable port forwarding is out of the question, as it should be. A simpler mechanism is to have a server on the internet that you control. It has a firewall with port forwarding setup. The clients are just clients, they connect to the server on a port and send and receive info about the current status of the game. That way, everyone has real-time updates on their local game engine. Plus, this way is much easier to program and implement.
No, TCP doesn't work like that.
The source port that has been used to talk to the rendezvous server will be transient and specific to that particular initial TCP socket connection and can only be used as a destination for return traffic on the same connection from the rendezvous server, and can't be used by a third party to make new inbound connections.
The typical (only?) practical solution when NATs are involved and port forwarding is not available is to have that central server relay all messages bidirectionally between the peers.
Hole punching is what I was looking for.
https://en.wikipedia.org/wiki/Hole_punching_(networking)
I use a static IP connection, Configured to TPLINK router.
I have a local server running which i can access from my network, but i want it to be accessed outside network.
So I did port forwarding. and its Successfully running.
Now the problem is :: The IP address of my WAN is also a private address like 10.10.X.X, so when am entering http://10.10.X.X, i can access my site, but not outside my network. Please guide me how to fix this?
If your WAN address is a private address, your ISP is using CGN. This is becoming more common since the RIRs have, or soon will, run out of public IP addresses to assign to ISPs. It sounds like your ISP has run out of public addresses and needs to use private addresses for its residential customers, reserving its remaining public addresses for its business customers which are willing to pay for public addresses.
Basically, your ISP is using NAT, too. You would need to have the ISP forward your port on its NAT router, but the odds of that are zero since it probably has a policy you agreed to to not host servers on your residential LAN (buried in the fine print of the ISP agreement). This situation will play out more and more over time.
You have to use the "Virtual Server" settings. Port triggering is used for.
Once the modem router is configured, the operation is as follows: 1. A local host makes an outgoing connection to an external host using a destination port number defined in the Trigger Port field. 2. The modem router records this connection, opens the incoming port or ports associated with this entry in the Port Triggering table, and associates them with the local host. 3. When necessary, the external host will be able to connect to the local host using one of the ports defined in the Incoming Ports field.
It is not used for incoming connections which are triggered from outside!
Of course, to have it working you have to have an application listening on that port not only having the firewall on Windows allowing the port.
After you set up the "Virtual Server" a port scanner should show you the port is open (even without having a running application listening) - it will try to port forward it. I use ShieldsUp for testing.
I am learning how to create an ubuntu server to use to host a database and run a script as a thread to do some things for my graduation project...
I installed ubuntu server with lamp environment and managed to connect it to an ethernet local network that connects to the internet .. my design looks like this
except the router is also connected to a dsl modem and to the internet...
I can easily connect to the server from the local network but how can I connect to it from outside this private network ?
I know the router public ip address and the server private ip address
You need port forwarding. mean, in your router settings you define that incoming requests to specific port/protocol will redirects to specific ip (of the ubuntu).
See https://en.wikipedia.org/wiki/Port_forwarding
You will need to set up port forwarding on the router such that the router's external port 80 is forwarded to the server's private port 80.
What router is it? Its guide should detail how to set up port forwarding
What I am asking is if two computers listen to the same port and a packet of information enters the router through the WAN Ip and the same port. Would the packet go to both computers? Neither? One or the other?
IE
computer 1 -(internal IP)-> 192.168.1.3 -(listens to port)-> 4444
computer 2 -(internal IP)-> 192.168.1.2 -(listens to port)-> 4444
computer 3 -(connects and sends)-> 24.157.358.45:4444
packet -> computer 1 AND computer 2
The code in VB6 is:
LAN.LocalPort = 4444
LAN.Protocol = sckTCPProtocol
LAN.Listen
I am using a WinSock object in the Microsoft WinSock Control 6.0 in VB6 Professional
If there is something that needs to be clarified I would be more than happy to.
The router won't send an inbound packet to either machine unless communication has already been established.
If 192.168.1.3 calls out to some other machine (e.g. 4.5.6.7) from its port 4444, the router will assign an arbitrary port on its external address (say 24.157.358.45 [sic] :5555) and pass the packets on to 4.5.6.7. 4.5.6.7 will send reply packets to 24.157.358.45:5555 -- because that's the only address it knows about -- and the router will relay those to 192.168.1.3:4444.
That's the normal course of things, but there are a lot of additional details to this scheme that make it possible to establish communication with a machine behind a router via trickery.
The system of having machines with private IP addresses behind a router with a public address is called network address translation (NAT); it's a pretty deep topic.
From my knowledge of routers, unless port forwarding is setup, the router will discard any packets sent on that port.
If port forwarding is setup, only one of the computers could be setup to receive the packets.
If the packet is an inbound request to establish a new TCP connection with a server that is running behind the router, the router must have an explicit port-forwarding rule configured, either statically in the router's configuration or dynamically via uPNP or SNMP, that tells the router where to route inbound packets on 24.157.358.45:4444 to, either to 192.168.1.2:4444 or to 192.168.1.3:4444, otherwise the packet will be discarded. So no, both of your listening servers will not see the same packet.
Once a TCP connection is established, the router knows which specific LAN machines are associated with which connections and will route incoming packets belonging to those connections accordingly.
The previous answers are correct, you need to enable port forwarding. If it is not enabled port 4444 will be closed on the router.
It sounds like you have multiple servers and want to forward to whatever server is turned on at the moment. This is not possible (*), the router does not care whether or not PC1 or PC2 are listening on port 4444, it will simply forward everything to the address configured in the port forwarding.
(*): Ok it is possible but it takes some extra work.
Solution 1: Trick the router into thinking there is only one server. Give PC1 and PC2 a virtual network interface with the same IP address and forward to that address. Make sure only one of these interfaces is enabled, having duplicate IP addresses in your network can have unintentional behaviour.
Solution 2: Make the router care about which server is on. You will need to write a program to run on the router (or on another server) that can detect which server is on and forward the packets accordingly. If you are using Linux the program iptables can be worth looking at.
If I have two internal computers connecting to the same external IP address through a NAT router, how is the router able to get the traffic to the correct internal computer? It is my understanding that NAT forwards incoming packets to the computer that recently sent outgoing packets to the [incoming packet's] sender's IP address. Since both computers are sending to the same address, does the router forward the packet to both? If that is the case, is it the responsibility of the client software to determine which packets are relevant?
Is it possible if both computers are attempting to connect to the same port?
When you open a socket, you need to address a port of the destination system and open a conjugate listening port on your own system to receive any response. You have to send the destination system your listening port.
Having more than one system using the same modem
When you start a web browser, and go to www.google.com:80, your browser obtains/searches for a free non-system conjugate port from the system for listening. Let us say, the conjugate port is 10000. The listener port is for receiving the http stream back from google.
Then your kid sitting next to you incidentally also browses www.google.com:80 and his/her google session of the play station or xbox-whatever also incidentally is assigned conjugate port 10000.
Both of you are sitting behind a cable modem, and behind the cable modem is your wireless router. And both of your systems are behind the wireless router - All sitting in that sequence, network topology-wise.
To prevent port address collision on the router/modem
Let us say that your cable company DHCP assigns your modem ip4 adress 72.72.72.72. But your wireless router DHCP assigns 192.168.0.10 to your system and to 192.168.0.11 to your kid's system.
When the frame carrying the information of your listener ports passes thro your NAT router, it would translate either one or both listening- ports. Let's say port 15000 for your page and port 16000 for your kid's page.
Your wireless router then sends your requests to google server as coming from 72.72.72.72:15000 and 72.72.72.72:16000.
The google server then responds individually to 72.72.72.72:15000 and 72.72.72.72:16000 and when you wireless router encounters the response, it reaches into the mapping that it has stored and translates 72.72.72.72:15000 to 192.168.0.10:10000 to reach your system but translates 72.72.72.72:16000 to 192.168.0.11:10000 to reach your kid's system.
Running web/game/ftp/etc servers
But what if you have a web server or an ftp server running on your system. What if you have two systems and both have a web server and both web servers are listening on port 80?
Let us say the local ip addresses registered/assigned with your wireless router of your first web server system is 192.168.0.30 and your second web server system is 192.168.0.40.
The wireless router would have a configuration web page usually by default 192.168.0.1:80, unless you changed it. There would be a tab to on the page where you could define/reserve application port mappings.
You could register with your wireless router to reserve the mapping
192.168.0.30:80 => outgoing port 8080
192.168.0.40:80 => outgoing port 8088
So that you have to phone your friends your web/game servers are addressable through
72.72.72.72:8080 and 72.72.72.72:8088 respectively,
where the wireless router would preclude its port 8080 and 8088 from its own dynamic NAT usage.
Of course, 72.72.72.72 is as good as only before your ISP DHCP decide to renew the ip4 address of your modem to say, 72.72.90.200. After which you would have to phone/email your friends and say
Hey, the servers' addresses have changed to 72.72.90.200:8080 and 72.72.90.200:8088 respectively. Or you could subscribe to dynamic dns (ddns) service to use a named domain where the ddns service will need you to install a simple heartbeat utility on your system to help them monitor the address variation. DDNS translation is a separate issue/strategy.
NAT modems
Newer ISP contracts supply you with a modem that has NAT. If so, you have to switch off either the one on your modem or the one on your wireless router. You should not use both - what's the point in translating twice because NAT is simply to prevent address collision. When you switch off NAT from your wireless router, it can operate as a hub switch and not a router anymore so that you could connect it to the modem using one of its LAN socket instead of thro its WAN socket.
The router manages "source" ports that are separate for each computer. While you may be connecting to port 80 on the "destination" the router may assign the source port to some high number port.
Wikipedia sums it up as
Network address translation involves
re-writing the source and/or
destination IP addresses and usually
also the TCP/UDP port numbers of IP
packets as they pass through the NAT.
Checksums (both IP and TCP/UDP) must
also be rewritten to take account of
the changes.
Already good answers are provided, but here is another example:
HOST A addr HOST B addr
10.1.0.2:4040 10.1.0.3:4040
-----------------------------------------
NAT 200.50.50.28:4040 200.50.50.28:4041 (what external host sees)
200.50.50.28 is router's global (internet) IP.
Every port number is unique in the NAT table. And of course the router does all the dirty job of modifying the source and destination addresses transparently.
It uses different ports for incoming external traffic, and the NAT then routes the packets on one port to one internal IP address, and the packets from the other port to the other internal IP address... The iniital request from each internal computer, when it goes through the NAT on the way out, establishes which port will be used for the incoming traffic from the external ip address, and it tells the external server what port to send it's traffic back on for that connection.
RFC3022 provides a lot of information on how this works
Since public facing or external IP Address that was given by Internet Service Provider (ISP) has been discussed, I would like to add on this.
You can ask your ISP to have your public IP Address not change. It will become static, so that you do not have to inform your friends to change the IP Address if they want to access your server inside your Network Address Translator (NAT).
As of this writing, static IP Address cost around 100 bucks. Most of the ISP they call it business account.
You can determine your public facing IP Address by googling "what is my ip address".