Packer loops through ports when attempting to establish SSH connection - ssh

Question

When Packer reaches the "Waiting for SSH to become available..." step.
My logs show
14:07:29 [INFO] Attempting SSH connection...
14:07:29 reconnecting to TCP connection for SSH
14:07:29 handshaking with SSH
14:07:29 handshake error: ssh: handshake failed: read tcp 127.0.0.1:60372->127.0.0.1:3057: read: connection reset by peer
14:07:29 [DEBUG] SSH handshake err: ssh: handshake failed: read tcp 127.0.0.1:60372->127.0.0.1:3057: read: connection reset by peer
14:07:36 [INFO] Attempting SSH connection...
14:07:36 reconnecting to TCP connection for SSH
14:07:36 handshaking with SSH
14:07:36 handshake error: ssh: handshake failed: read tcp 127.0.0.1:60376->127.0.0.1:3057: read: connection reset by peer
14:07:36 [DEBUG] SSH handshake err: ssh: handshake failed: read tcp 127.0.0.1:60376->127.0.0.1:3057: read: connection reset by peer
Note a different port on each attempt.
60372
60376
Packer is trying a new port, every 7 seconds.
Is there a way to configure the ports before or during the build to avoid this try/fail approach?

Answer 1

That is the source port which the ssh connection is made from. It's assigned by the OS with a random available high port.

Answer 2

The issue is not with SSH Server or TCP/IP. It is with the way Packer is designed.
When a VM is created, Packer.io will run boot commands. It takes time and time varies on different machines. During that time you will see "Waiting for SSH to become available...". On the background, Packer.io will be attempting to establish an SSH connection. The log is saturated with messages like this
Linux
14:07:29 [INFO] Attempting SSH connection...
14:07:29 reconnecting to TCP connection for SSH
14:07:29 handshaking with SSH
14:07:29 handshake error: ssh: handshake failed: read tcp 127.0.0.1:60372->127.0.0.1:3057: read: connection reset by peer
14:07:29 [DEBUG] SSH handshake err: ssh: handshake failed: read tcp 127.0.0.1:60372->127.0.0.1:3057: read: connection reset by peer
or
Windows
15:54:31 packer.exe: 2017/02/01 15:54:31 [INFO] Attempting SSH connection...
15:54:31 packer.exe: 2017/02/01 15:54:31 reconnecting to TCP connection for SSH
15:54:31 packer.exe: 2017/02/01 15:54:31 handshaking with SSH
15:54:31 packer.exe: 2017/02/01 15:54:31 handshake error: ssh: handshake failed: read tcp 127.0.0.1:62691->127.0.0.1:4289: wsarecv: An existing connection was forcibly closed by the remote host.
15:54:31 packer.exe: 2017/02/01 15:54:31 [DEBUG] SSH handshake err: ssh: handshake failed: read tcp 127.0.0.1:62691->127.0.0.1:4289: wsarecv: An existing connection was forcibly closed by the remote host.
OS will boot and with it SSH server on the guest will become available. At that moment SSH connection from host to guest should establish.
Reproduced and Confirmed on Windows 10 Pro and Ubuntu 16.04.1 TLs