I have created simple Java application which sends emails. It's working properly when I running it from my IDE, but when running it inside a Docker container it can't reach the remote SMTP server. I'm using
docker run -d -p 25:25 [image]:[tag]
to expose port 25 when starting the container. Does anyone has an idea why the mail client can't connect?
I think you are confusing the point of the port mapping. This is to allow the host to bind the specified port on the given network interface to the port in the container. In your case you are trying to connect to port 25 i presume on another remote host.
If the app works when run in the IDE I'd assume either an issue resolving the SMTP server or a problem with the address on which the SMTP server is listening.
Are you running the SMTP server locally or connecting to one that is resolvable via public DNS? If you use docker exec to enter the running container can you telnet to the SMTP server?
Related
Hi what I am actually trying is to connect remotly from a MySQL Client in Windows Subsystem for Linux mysql -h 172.18.0.2 -P 3306 -u root -p and before that I started the Docker Container as follows: docker container run --name testdb --network testnetwork -p 3306:3306 -e MYSQL_ROOT_PASSWORD=mysqlRootPassword -e MYSQL_DATABASE=localtestdb -d mariadb/server.
The purpose why I put the container in a own network, is because I also have a dockerized Spring Boot Application (GraphQL-Server) which shall communicated with this db. But always when I try to connect from my built-in mysql client, in my Windows Subsystem for Linux, with the above shown command. I got the error message: ERROR 2002 (HY000): Can't connect to MySQL server on '172.18.0.2' (115).
What I already tried, to solve the problem on my own is, look up whether the configuration file line (bind-address) is commented out. But it wont work. Interestingly it already worked to set up a docker container with MariaDB and connect from the outside, but now when I try exactly the same, only with the difference that I now put the container in a own existing network, it wont work.
Hopefully there some one out there which is able to help me with this annonying problem.
Thanks!
So far,
Daniel
//edit:
Now I tried the solution advice from a guy from this topic: How to configure containers in one network to connect to each other (server -> mysql)?. Futhermore I linked my Spring Boot (server) application with the "--link databaseContainerName" parameter to the MariaDB container.
Now I am able to start both containers without any error, but I am still not able to connect remotly to the MariaDB container. Which is now running in a virtual docker network with his own subnet.
I explored this recently - this is by design - container isolation. Usually only main (service httpd) host is accessible externally, hiding internal connections (hosts it communicates to deliver response).
Container created in own network is not accessible from external adresses, even from containers in the same bridge but other network (172.19.0.0/16).
Your container should be accessible on docker host address (127.0.0.1 if run locally) and mapped ("-p 3306:3306") port - 3306. But of course it won't work if many running db containers have the same mapping to the same host port.
Isolation is done using firewall - iptables. You can list rules (iptables -L) to see that - from docker host level.
You can modify firewall to allow external access to internal networks. I used this rule:
iptables -A DOCKER -d 172.16.0.0/12 -j ACCEPT
After that your MySQL containerized engine should be accessible using internal address 172.18.0.2 and source (not mapped) port 3306.
Warnings
it disables all isolation, dont't use it on production;
you have to run this after every docker start - rules created/modified by docker on the fly
not every docker container will respond on ping, check it from docker host (linux subsystem in this case) first, from windows cmd later
I used this option (in docker.service) to make rule permanent:
ExecStartPost=/bin/sh -c '/etc/iptables/accept172_16.sh'
For docker on external(shared in lan) host you should use route add (or hosts file on your machine or router) to forward 172.x.x.x addresses into lan docker host.
Hint: use portainer project (with restart policy - always) to manage docker containers. It's easier to see config errors, too.
I have set up a couple of containers that interact with each other. The main application container runs on --network = host because it queries several mySQL containers running on different ports exposed on the host network.
I am trying to hit the application on the host but get an error:
curl: (7) Failed to connect to 0.0.0.0 port 36081: Connection refused
I am working on Docker installed on MacOS.
I have read several questions that indicate that docker on MacOS runs on a VM. But what is the workaround to access the application from the host? Any way to get the IP of the said VM?
You cannot use --network=host on Mac to connect via host ports but binding to host port using -p options works.
https://docs.docker.com/docker-for-mac/networking/#/there-is-no-docker0-bridge-on-osx
I WANT TO CONNECT TO A CONTAINER FROM THE MAC
Port forwarding works
for localhost; --publish, -p, or -P all work. Ports exposed from Linux
are forwarded to the host.
Our current recommendation is to publish a port, or to connect from
another container. This is what you need to do even on Linux if the
container is on an overlay network, not a bridge network, as these are
not routed.
For your use case,
You need to create a docker network and attach both the DB and application containers to this network. Then the containers will be able to talk to each other by their name. You can also publish the application container port so that you can access it from your host.
https://docs.docker.com/network/bridge/
Instead of creating the network, attaching the containers to the network etc manually, you can use docker-compose.
https://docs.docker.com/compose/
I am running a web application(copied from github examples) that is running as a container in a remote ubuntu VM. The application is a Node JS application that is using mysql database. I brought the application up using docker-compose in ubuntu.
The application came up as http://172....:3000 using a network port. The ip address is displayed in the docker-compose terminal. In the ubuntu system, when i do curl http://172....:3000, it gives a proper success response. The ip address is a container network address. It is not the VM's ip address. There is no firewall.
How to access the web application from my windows 7 machine. When I tried accessing using http://VM Ip address:3000, it is not hitting ubuntu system. I am not getting any message in the docker-compose terminal. Can anyone help here ?
ports:
- "3031:3000"
similar line in your docker compose means you have published port 3000 of your container to port 3031 of your Ubuntu VM.
now you can access your client service as http://<ubuntu-ip>:3031 but before this, you need to allow access to port 3031
I have a Windows Server 2016 TP5 machine that I use as a container host.
I have a Windows Container running that I manage with Docker. Inside this container I have an Apache httpd running on port 88.
The port mapping when I start the container is: 0.0.0.0:80->88/tcp, so I map port 80 of my container host to port 88 of the container.
This is the output from docker inspect: http://pastebin.com/AVem1eGV
I can now reach the Apache http start page from any other computer in the network through the DNS or IP.
In my case:
http://10.10.1.162/
http://documents.test2016-3.company.com/
But the same does not work when I try to call the same from the host system itself or from inside the container. So, on the host system, I try to access the same URL via browser or wget, and getting:
C:\> wget -UseBasicParsing http://documents.test2016-3.company.com/
wget : Unable to connect to the remote server
in both cases.
But I can ping the host from both the host itself as well as the container.
From the host:
C:\>ping test2016-3.company.com
Ping wird ausgeführt für TEST2016-3.company.com [fe80::847a:1430:8a10:b120%4] mit 32 Bytes Daten:
From the container:
PS C:\> ping documents.test2016-3.company.com
Pinging documents.test2016-3.company.com [10.10.1.162] with 32 bytes of data:
which seems to be able to resolve the name just fine.
What does work though is to call the Apache default page via the container hostname (which is win-de6u4068naf) and its running port directly (not through the port mapping), both from the host as well as inside the container:
http://win-de6u4068naf:88/
Just going the route through the container host hostname and mapped port from the host or container itself does not work properly!
Firewall rules allow everything on port 80 from any remote address or to port 80 (=inbound and outbound rules are both set to "allow" for "any").
I know that Microsoft/Docker changed the networking code base of the container/docker support from Windows Server 2016 TP4 to TP5. Not sure if that's related, or whether this is a bug or I'm having something not configured correctly yet.
I made a test and left Docker/Container out of the picture above and installed a plain Apache httpd itself on the container host system on port 80 (and no Docker running at all) just to check whether such setup works or not, in order to be sure that it is actually somehow Docker/Container related and not a problem with my network/host configuration in general. And this works fine, I can reach the Apache from outside as well as from the host itself, thus it must be a Docker/Container related problem.
Environment:
Windows Server 2016 TP5
Docker version 1.12.0-dev, build 2b97201
Got a reply on Microsoft's Github:
https://github.com/Microsoft/Virtualization-Documentation/issues/253#issuecomment-217975932
This is a known limitation in our Windows NAT implementation (WinNAT)
that you cannot access the external port in a static port mapping
directly from the container (NAT) host.
I'm using Boot2Docker to manage Docker containers in Windows and I have a container running an IBM Liberty server (I guess is the same for any other server), I can access the server home screen in the host machine using only the ip (which I get using the command boot2docker ip), but if I try to access the server using the https port, like this xx.xx.xx.xx:9443 the connection fails.
I tried forwarding the port in VirtualBox like this:
And then access the server using the ports 1000 or 1001, but it fails too.
Am I missing something?
BTW, I'm using default NAT connection.
https uses port 443 (not 9443) by default.
Make both "Host Port" and "Guest Port" 443 and try again.