CODEWITHSUNDEEP
node.jsdebuggingdockerport
Citronen
Citronen

Reputation: 4490

Opening Port in Docker Container

I'm attempting to run a node.js application in debug mode in one Docker container, and attach a debugger from another container onto the application running in the first container.

As such, I'm trying to open up port 5858 to the outside world. However, when I --link another container to the first container (with alias firstContainer), and run nmap -p 5858 firstContainer, I find that port 5858 is closed. The first container has told me that the node.js application is listening on port 5858, I've exposed the port in the Dockerfile, and I've also bound the ports to the corresponding port on my machine (although, I'm not certain that's necessary). When I run nmap on port 8080, all is successful.

How can I open up port 5858 on a Docker container such that I can attach a debugger to this port?

The Dockerfile is:

FROM openshift/base-centos7

# This image provides a Node.JS environment you can use to run your Node.JS
# applications.

MAINTAINER SoftwareCollections.org <[email protected]>

EXPOSE 8080 5858

ENV NODEJS_VERSION 0.10

LABEL io.k8s.description="Platform for building and running Node.js 0.10 applications" \
      io.k8s.display-name="Node.js 0.10" \
      io.openshift.expose-services="8080:http" \
      io.openshift.tags="builder,nodejs,nodejs010"

RUN yum install -y \
    https://www.softwarecollections.org/en/scls/rhscl/v8314/epel-7-x86_64/download/rhscl-v8314-epel-7-x86_64.noarch.rpm \
    https://www.softwarecollections.org/en/scls/rhscl/nodejs010/epel-7-x86_64/download/rhscl-nodejs010-epel-7-x86_64.noarch.rpm && \
    yum install -y --setopt=tsflags=nodocs nodejs010 && \
    yum clean all -y

# Copy the S2I scripts from the specific language image to $STI_SCRIPTS_PATH
COPY ./s2i/bin/ $STI_SCRIPTS_PATH

# Each language image can have 'contrib' a directory with extra files needed to
# run and build the applications.
COPY ./contrib/ /opt/app-root

# Drop the root user and make the content of /opt/app-root owned by user 1001
RUN chown -R 1001:0 /opt/app-root
USER 1001

# Set the default CMD to print the usage of the language image
CMD $STI_SCRIPTS_PATH/usage

Run with:

docker run -P -p 5858:5858 -p 8080:8080 --name=firstContainer nodejs-sample-app

Taken from/built with instructions from here.

Thanks.

Upvotes: 2

Views: 4577

Answers (1)

carter
carter

Reputation: 5442

-P automagically maps any exposed ports within a container to a random port on host machine, while -p allows explicit mapping of ports. Using the --link flag allows two docker containers to communicate with each other, but does nothing to expose the ports to the outside world (outside the docker private network).

Upvotes: 3

Related Questions