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Previously, we implemented accessing services running in docker containers through network ports. Network applications can run in containers, and to allow external access to these applications, you can use the **-P** or **-p** parameter to specify port mapping. Below we will implement connecting to a docker container through ports. * * * ## Network Port Mapping We created a python application container. tutorial@tutorial:~$ docker run -d -P training/webapp python app.py fce072cc88cee71b1cdceb57c2821d054a4a59f67da6b416fceb5593f059fc6d Additionally, we can specify the network address to bind the container to, for example binding to 127.0.0.1. We use **-P** to bind the port number, and using **docker ps** you can see container port 5000 is bound to host port 32768. tutorial@tutorial:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper We can also use the **-p** flag to specify container port binding to a host port. The difference between the two methods is: * **-P:** Maps container internal ports **randomly** to host ports. * **-p:** Binds container internal ports to **specified** host ports. tutorial@tutorial:~$ docker run -d -p 5000:5000 training/webapp python app.py 33e4523d30aaf0258915c368e66e03b49535de0ef20317d3f639d40222ba6bc0 tutorial@tutorial:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper Additionally, we can specify the network address to bind the container to, for example binding to 127.0.0.1. tutorial@tutorial:~$ docker run -d -p 127.0.0.1:5001:5000 training/webapp python app.py 95c6ceef88ca3e71eaf303c2833fd6701d8d1b2572b5613b5a932dfdfe8a857c tutorial@tutorial:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 95c6ceef88ca training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5001->5000/tcp adoring_stonebraker 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper This way we can access the container's port 5000 by visiting 127.0.0.1:5001. In the examples above, TCP ports are bound by default. To bind a UDP port, add **/udp** after the port. tutorial@tutorial:~$ docker run -d -p 127.0.0.1:5000:5000/udp training/webapp python app.py 6779686f06f6204579c1d655dd8b2b31e8e809b245a97b2d3a8e35abe9dcd22a tutorial@tutorial:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 6779686f06f6 training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5000->5000/udp drunk_visvesvaraya 95c6ceef88ca training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5001->5000/tcp adoring_stonebraker 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper The **docker port** command allows us to quickly check port binding status. tutorial@tutorial:~$ docker port adoring_stonebraker 5000127.0.0.1:5001 * * * ## Docker Container Connection Port mapping is not the only way to connect docker to another container. Docker has a linking system that allows multiple containers to be connected together, sharing connection information. Docker linking creates a parent-child relationship, where the parent container can see information about the child container. * * * ### Container Naming When we create a container, docker automatically assigns it a name. Additionally, we can use the **--name** flag to name the container, for example: tutorial@tutorial:~$ docker run -d -P --name tutorial training/webapp python app.py 43780a6eabaaf14e590b6e849235c75f3012995403f97749775e38436db9a441 We can use the **docker ps** command to view container names. tutorial@tutorial:~$ docker ps -l CONTAINER ID IMAGE COMMAND ... PORTS NAMES 43780a6eabaa training/webapp "python app.py" ... 0.0.0.0:32769->5000/tcp tutorial ### Create a Network First, create a new Docker network below. $ docker network create -d bridge test-net !(#) Parameter description: **-d**: The parameter specifies the Docker network type, which can be bridge or overlay. The overlay network type is used for Swarm mode, you can ignore it in this section. ### Connect Containers Run a container and connect it to the test-net network: $ docker run -itd --name test1 --network test-net ubuntu /bin/bash Open a new terminal and run another container and join it to the test-net network: $ docker run -itd --name test2 --network test-net ubuntu /bin/bash Click