This post is a continuation of the previous post called FileZilla FTP Introduction. In this post I will discuss some technical information that is on the Help of FileZilla. FTP is File Transfer Protocol.
Networks vary considerable in their configuration. There are too many combinations to list. The only way to understand computer networks is to understand the underlying principals and technical setups. Troubleshooting network issues can be difficult. You need to understand the principals and use logic, such as the process of elimination for example, to fix the problem. There is Help available at the FileZilla Wiki page for Network Configuration.
At the Wiki it says: “It is important to understand the basics of the FTP protocol in order to configure FileZilla and the routers and/or firewalls involved.” This post is based on the Network Configuration article.
The FileZilla Wiki says: “When you connect to an FTP server, you are actually making two connections. First, the so-called control connection is established, over which FTP commands and their replies are transferred. Then, in order to transfer a file or a directory listing, the client sends a particular command over the control connection to establish the data connection. The data connection can be established two different ways, using active mode or passive mode.”
Passive or Active Mode
FileZilla Wiki says: “In passive mode, which is recommended, the client sends the PASV command to the server, and the server responds with an address. The client then issues a command to transfer a file or to get a directory listing, and establishes a secondary connection to the address returned by the server. In active mode, the client opens a socket on the local machine and tells its address to the server using the PORT command. Once the client issues a command to transfer a file or listing, the server will connect to the address provided by the client. In both cases, the actual file or listing is then transferred over the data connection.”