.testConnection() blocks indefinitely

[sddavis]

A call to org.simplejavamail.mailer.Mailer.testConnection() with a session timeout of 60s blocked for 3 hours before the user gave up and killed the process. This was using SMTP on port 25 with simple-java-mail-5.0.3.jar.

Thread dump:

at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:171) at java.net.SocketInputStream.read(SocketInputStream.java:141) at com.sun.mail.util.TraceInputStream.read(TraceInputStream.java:126) at java.io.BufferedInputStream.fill(BufferedInputStream.java:246) at java.io.BufferedInputStream.read(BufferedInputStream.java:265) at com.sun.mail.util.LineInputStream.readLine(LineInputStream.java:104) at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:2425) at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2172) at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:726) at javax.mail.Service.connect(Service.java:388) at javax.mail.Service.connect(Service.java:246) at javax.mail.Service.connect(Service.java:195) at org.simplejavamail.mailer.internal.mailsender.MailSender.testConnection(MailSender.java:380) at org.simplejavamail.mailer.Mailer.testConnection(Mailer.java:222)

[sddavis]

I see that at https://github.com/bbottema/simple-java-mail it says "You can now test the connection to the SMTP server" in v5.1.0 with a link to #179, which seems completely unrelated to testing connections. But the test connection feature is present in v5.0.3, so I don't understand what this means.

Did something related to testing connections change in v5.1.0 that might help here?

[sddavis]

Possibly related to #182?

[bbottema]

Possibly related to #182?

I agree, this is probably related.

Are you able to get the timeout working with good old manual Session properties?

[sddavis]

I have not been able to reproduce the problem myself. I don't know what condition triggers the timeout being ignored.

[bmuskalla]

I've been able to reproduce this issue using a plain socket server that does not respond at all. I can verify that using the manual session properties works. Here is a test case to reproduce both ways:
https://gist.github.com/bmuskalla/17d789716494d8ceb331bd02fb45c9dd

I think the problem is that MailSender#configureSessionWithTimeout is only ever called by #send but not by test connection. This leads to a session for connection tests without the timeouts.
Happy to provide a pull request with a fix if you can point me to the location where I can get the parent pom (maven-master-project) from.

[bbottema]

Ahh, I was not thinking of this as a problem specific to testConnection. Your assessment is probably correct, @bmuskalla. For this I would create a hotfix branch off of master to create a patch for this. The master is not yet modularized, so no parent POM needed there.

[bbottema]

Started working on a fix...

[bbottema]

Fix released in 5.1.2, can you please verify, @sddavis, @bmuskalla?