When using FTP through an HTTP Proxy, be aware that some HTTP proxies now include a configuration parameter called AllowCONNECT. This parameter lists the ports through which the HTTP Proxy allows outgoing connections when an HTTP CONNECT command is received. When you FTP through an HTTP Proxy, the FTP process uses passive mode. In passive mode, after the initial FTP connection, the FTP process receives a port number from the FTP server. The FTP server wants the client to use this port number when establishing a second connection, the data connection, to the FTP server. If this port number is not in the AllowCONNECT port list in the HTTP Proxy configuration, then the proxy does not allow the second connection to be established with the FTP server. Some FTP servers, as part of their configurations, allow the ports returned to the client to be restricted to a certain range. In this case, you must add all the port numbers within the range to the AllowCONNECT HTTP Proxy directive for the FTP session to connect through the HTTP Proxy.