Dockerfile with the one-line nc-based webserver

Dockerfile

FROM busybox:latest

ENV port=8081

RUN \
    echo -e 'echo $port\n\nwhile true\ndo\n    (echo -e "HTTP/1.1 200 OK\\nContent-Type: text/html\\n\\n<b>Hello World</b><br>Builded at $(date)";) | nc -vv -l -p $port\ndone' > server.sh \
    && chmod +x server.sh \
    && mkdir /var/log

EXPOSE 8081:8081

ENTRYPOINT port=$port ./server.sh