I am running a web server (Java Spring boot application) inside a Docker container on port 8080, which is exposed to interface 127.0.0.1 also on port 8080.
docker ps shows that the port is exposed:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a055dd0dbbfe image "/bin/sh -c 'echo \"T…" 39 minutes ago Up 39 minutes 127.0.0.1:8080->8080/tcp my-app_1
netstat -an in the host shows the port is actually listening:
tcp 0 0 127.0.0.1:8080 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:35900 127.0.0.1:8080 FIN_WAIT2
tcp 142 0 127.0.0.1:8080 127.0.0.1:35900 CLOSE_WAIT
tcp 0 1 172.18.0.1:36626 172.18.0.3:8080 SYN_SENT
If I try to access the server from the Docker host
wget 127.0.0.1:8080
I can see that the connection is established, the HTTP request is sent, but no response is received. The connection is closed by peer after a time. This behavior is reflected in tcpdump as well:
21:01:14.174522 IP localhost.35872 > localhost.http-alt: Flags [S], seq 441189964, win 43690, options [mss 65495,sackOK,TS val 342973 ecr 0,nop,wscale 7], length 0
21:01:14.174546 IP localhost.http-alt > localhost.35872: Flags [S.], seq 3411015394, ack 441189965, win 43690, options [mss 65495,sackOK,TS val 342973 ecr 342973,nop,wscale 7], length 0
21:01:14.174570 IP localhost.35872 > localhost.http-alt: Flags [.], ack 1, win 342, options [nop,nop,TS val 342973 ecr 342973], length 0
21:01:14.176050 IP localhost.35872 > localhost.http-alt: Flags [P.], seq 1:142, ack 1, win 342, options [nop,nop,TS val 342973 ecr 342973], length 141: HTTP: GET / HTTP/1.1
21:01:14.176068 IP localhost.http-alt > localhost.35872: Flags [.], ack 142, win 350, options [nop,nop,TS val 342973 ecr 342973], length 0
21:03:21.418268 IP localhost.http-alt > localhost.35872: Flags [R.], seq 1, ack 142, win 350, options [nop,nop,TS val 374784 ecr 342973], length 0
The webserver in the container works. Spring Boot server listens to all interfaces (lo and eth0):
Application 'app' is running! Access URLs:
Local: http://127.0.0.1:8080
External: http://172.18.0.3:8080
and I can successfully wget from inside the container:
docker exec <container> wget localhost:8080:
Connecting to localhost:8080 (127.0.0.1:8080)
index.html 100% |*******************************| 12560 0:00:00 ETA
Docker version is 18.09.2 for client and engine.
OS is Ubuntu, uname -a:
Linux srv02 4.4.0-142-generic #168-Ubuntu SMP Wed Jan 16 21:00:45 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
I have no idea what could be wrong?
localhost- by outside, you mean a different machine? Or you mean "outside the container from the host running the container?" What is localhost mapped to? Did you try 127.0.0.1:8080?loandeth0on port 8080. Changed "from outside" to "from the Docker host".localhostis mapped to 127.0.0.1, I also tried without DNS.