Docker Container doesn't answer to another container requests

Question

I'm starting using docker. I'm creating a COAP application with a client and a server. In this application, a client sends a simple request and the server has to response to it. I built my image that runs my code in node.js. Then I used a docker-compose.yml file that I will show you in the code section. However, it seems like the server doesn't respond to the client request.

I tried to see if the IP address were well assigned, and everything seems ok. I also tried to use Wireshark on docker0 and I can see the coap packets going from the client to the server, but I don't have an answer. Here is the docker-compose.yml

services:
 Server_Coap:
  build: './Server_Coap'
  image: 'user/mynode:latest'
  container_name: server
  ports: 
  - "8081:5683"
  networks:
   rete:
    ipv4_address: 172.19.0.3
networks:
 rete:
   ipam:
    driver: default
    config:
     - subnet: 172.19.0.0/24

Here is the client code:

const coap = require('coap'),
req = coap.request('coap://172.19.0.3')
console.log("Client Request...")
req.on('response' , function(res){
    res.pipe(process.stdout)
})

req.end()

Here is the server code:

var coap = require('coap')
,server = coap.createServer()


server.on('request' , function(req, res){
    console.log("New request")
    res.end('Hello ' + req.url + '\n')
})

// the default CoAP port is 5683
server.listen(function() {
    console.log("Server started")
  })

Here is my Dockerfile for the server:

FROM node:latest

WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install 
COPY . .
EXPOSE 5683
CMD ["node" , "server.js"]

Here is my Dockerfile for the client:

FROM node:latest 

WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 5683
CMD ["node" , "client.js"]

I would like to have an answer from the server. This is the kind of error that I get: │ Error: No reply in 247s │ at Timeout._onTimeout (/usr/src/app/node_modules/coap/lib/retry_send.js:74:16) │ at listOnTimeout (internal/timers.js:531:17) │ at processTimers (internal/timers.js:475:7) │ Emitted 'error' event on OutgoingMessage instance at: │ at RetrySend.emit (events.js:209:13) │ at Timeout._onTimeout (/usr/src/app/node_modules/coap/lib/retry_send.js:77:12) │ at listOnTimeout (internal/timers.js:531:17) │ at processTimers (internal/timers.js:475:7) { │ retransmitTimeout: 247

Marcos Luis Delgado · Accepted Answer · 2019-09-12T10:30:47.683

2

You have to add your client docker to the network. IE:

services:
 Server_Coap:
  build: './Server_Coap'
  image: 'user/mynode:latest'
  container_name: server
  ports: 
  - "8081:5683"
  networks:
   rete:
    ipv4_address: 172.19.0.3
 Client_Coap:
  build: './Client_Coap'
  image: 'user/mynode:latest'
  container_name: client
  networks:
   rete
networks:
 rete:
   ipam:
    driver: default
    config:
     - subnet: 172.19.0.0/24

edited Sep 12 '19 at 10:30

answered Sep 12 '19 at 10:09

Marcos Luis Delgado

1,289
7
11

My client is another docker container – Andrea Fresa Sep 12 '19 at 10:15
I updated my question with the requested Dockerfile. – Andrea Fresa Sep 12 '19 at 10:23
Why should I do that if I'm using an Internet application? – Andrea Fresa Sep 12 '19 at 10:25
Ok, I will try your idea and I will see what happens. Thanks btw ;) @Marcos Luis – Andrea Fresa Sep 12 '19 at 10:28
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/199364/discussion-between-marcos-luis-and-andrea-fresa). – Marcos Luis Delgado Sep 12 '19 at 10:31
1

I used this solution and it worked. Thanks @Marcos Luis – Andrea Fresa Sep 13 '19 at 13:25

Adiii · Answer 2 · 2019-09-12T10:33:30.913

Remove the unnecessary network setting from the docker-compose.

services:
 Server_Coap:
  build: './Server_Coap'
  image: 'user/mynode:latest'
  container_name: server
  ports: 
  - "8081:5683"

And modify this to localhost, I assume they are running in the same container. If you want to access from out side then you need to mention publish port 8081.

const coap = require('coap'),
req = coap.request('coap://localhost')
console.log("Client Request...")
req.on('response' , function(res){
    res.pipe(process.stdout)
})

req.end()

If the coap client in other containers, better to place them in single compose file and will both able to talk on same network.
If the coap is running on the host, outside of container then you can use localhost:8081 on client-side to connect.
if the coap is running in different container, use the host ip in client side. host_ip:8081 to connect from the client.

To connect from a different network inside the only way to connect from host ip with publishing port, otherwise, it will not accessible to the client.

docker run --add-host=coab-server:YOUR_HOST_IP --rm -it coad-client

After this modify client.

req = coap.request('coap://coab-server')

Also would suggest to expose same port "5683:5683", if you do not want to use network, as I am not able see to port option or you can try.

req = coap.request('coap://coab-server')

or with current port

req = coap.request('coap://coab-server:8081')

Client and server are 2 different docker container. I create a network because I want a static ip for my server. — Andrea Fresa, Sep 12 '19 at 10:16
updated. `Add entries to container hosts file (--add-host)` https://docs.docker.com/engine/reference/commandline/run/ — Adiii, Sep 12 '19 at 10:33

score 0 · Answer 3 · answered Sep 19 '19 at 20:04

0

Usually CoAP over UDP is used, so the ports must be classified as udp

 ports: 
  - "8081:5683/udp"

answered Sep 19 '19 at 20:04

Achim Kraus

729
1
7
11

Docker Container doesn't answer to another container requests

3 Answers3