docker 容器内的 C# FTP 服务器 - 连接问题

Question

I'm not able to connect to docker container ftp server. Here is my docker file:

FROM mcr.microsoft.com/dotnet/sdk:5.0-alpine AS build
WORKDIR /app
COPY . ./
RUN dotnet publish MD.Ftp.Server -c Release -o out -r linux-x64 
FROM mcr.microsoft.com/dotnet/runtime:5.0
WORKDIR /app
COPY --from=build /app/out .
ENTRYPOINT ["dotnet", "MD.Ftp.Server.dll"]
EXPOSE 6001/tcp

To run FTP server I create TcpListener the following way:

tcpListener = new TcpListener(new IPEndPoint(IPAddress.Any, settings.Port));

When I run it locally from the IDE I can connect to it using FileZilla. When I run it inside a container - no luck. What am I doing wrong?

FileZilla logs:

Status:         Disconnected from server
Status:         Connecting to 127.0.0.1:6001...
Status:         Connection established, waiting for welcome message...
Status:         Plain FTP is insecure. Please switch to FTP over TLS.
Status:         Logged in
Status:         Retrieving directory listing...
Command:    PWD
Response:   257 "/"
Command:    TYPE I
Response:   200 In IMAGE type
Command:    PASV
Response:   227 Enter Passive Mode (172,17,0,2,234,142)
Command:    LIST
Response:   150 File is Ok, about to open connection.
Error:          Connection timed out after 20 seconds of inactivity
Error:          Failed to retrieve directory listing
Status:         Disconnected from server
Status:         Connecting to 127.0.0.1:6001...
Status:         Connection established, waiting for welcome message...
Status:         Plain FTP is insecure. Please switch to FTP over TLS.
Status:         Logged in
Status:         Retrieving directory listing...
Command:    PWD
Response:   257 "/"
Command:    TYPE I
Response:   200 In IMAGE type
Command:    PASV
Response:   227 Enter Passive Mode (172,17,0,2,234,143)
Command:    LIST
Response:   150 File is Ok, about to open connection.
Error:          Connection timed out after 20 seconds of inactivity
Error:          Failed to retrieve directory listing

However I don't see anything in the application logs... Not sure what's happening

Answer 1

how do you run your container? You should publish your port as well as exposing. Expose is a docker-inside concept and publish is out of docker one. I mean:

docker run -d -p 6001:6001 YOUR_IMAGE_NAME

As you may know, FTP protocol has two types, ACTIVE and PASSIVE. You should open at least 10 ports from X to Y (range) to let your client access your FTP server using default FTP commands. I highly recommend you to see this article https://www.jscape.com/blog/bid/80512/active-vs-passive-ftp-simplified

Answer 2

Hi having the same problem and I figured out why but not how to solve it.

You have two connections, one is the controlconnection and the other is your dataconnection and they need to have the same IP obviously.

So now I don't know your code but based on the output your controlconnection is getting the IP 127.0.0.1 but your dataconnection is getting the IP of the container 172.17.0.2. and since the two connections aren't the same IP the server shuts down the connection.