Error Messages

Network error: Connection refused
Network error: Connection timed out
Network error: No route to host
Host does not exist
Connection has been unexpectedly closed. Server sent command exit status 1
Received too large (??? B) SFTP packet. Max supported packet size is 102400 B
Invalid access to memory

Network error: Connection refused

You may get this message when connecting to a server for following reasons:

You are trying to use WinSCP for a purpose for which it is not designed. WinSCP needs a SSH or FTP server to be installed at the other end (on the machine you want to connect to). In particular, you cannot easily use it to connect to another Windows workstation, since Windows does not have an SSH or FTP server included by default.
You are trying to use protocol that the server does not support. Particularly you are trying SFTP/SCP (over SSH), but the server supports FTP; or vice versa. Check selected protocol on login dialog.
The server is running on non-standard port. Please make sure you enter actual port number of login dialog.
You may need to connect through proxy server, but you have not specified one on login dialog.
Connection was blocked by firewall. Please refer to FAQ.

If you are trying to use WinSCP to connect to your iPhone or iPod Touch, please refer to FAQ.

Network error: Connection timed out

All reasons and hints for “Network error: Connection refused” above apply to this error too.

Network error: No route to host

All reasons and hints for “Network error: Connection refused” above apply to this error too.

Host does not exist

You may get this message when connecting to a server for following reasons:

You may have typed a wrong hostname on Login dialog.
Your domain name is new and is not fully distributed to DNS servers yet.
Connection was blocked by firewall. Please refer to FAQ.

Connection has been unexpectedly closed. Server sent command exit status 1

If you get this error message while logging into your server, it is most usually cause by the server not being able to run some process necessary to support your session. Possibilities are:

Shell. Your account may not be allowed to start a shell at all. With some servers (like OpenSSH), you may need to be allowed to start a shell, even if using SFTP protocol.
SFTP server. Your account may not be able to start SFTP server binary (e.g. /bin/sftp-server) or the binary is not present on your server. Your SSH server may also lack the SFTP subsystem.

Received too large (??? B) SFTP packet. Max supported packet size is 102400 B

If ??? (from the subject) is a very large number then the problem is typically caused by a message printed from some profile/logon script. It violates the SFTP protocol. Some of these scripts are executed even for non-interactive (no TTY) sessions, so they cannot print anything (nor ask user to type something).

The number ??? represents the first four bytes read from the server. If your login scripts are printing words, this will be the first four characters cast into a number, and not an SFTP message at all.

To fix the problem find out what command in your login script prints text. Once you find it move the command to the proper interactive script, or remove it entirely. The scripts are usually hidden (their name starts with dot) and are located in your home directory on the server.

There are other possible sources of the message in addition to the profile script - some SSH servers print messages if they are unable to start the SFTP server, or encounter a fatal error. You should contact your server administrator.

Another possibility is that the server is configured to only allow the SCP protocol and not the SFTP protocol, in such a way that SCP fallback mechnism of WinSCP does not work. The solution is to choose SCP protocol on the login dialog.