Then the FTP Server initiates another TCP three-way handshake back to FTP Client at the IP address and the port number specified in FTP PORT command. Once the user authentication is completed, FTP Clients sends the FTP PORT command to inform the FTP Server the IP address and the TCP port the FTP Client is using for Data Channel connection. Typically, this is one port above the Control channel port used by the FTP Client. FTP Client opens a TCP port at client computer and then starts listening to it for FTP Data channel connection. The interesting thing in FTP Active mode connection happens now. FTP Client uses a random port number above 1023 (above well-known port range) for FTP Control channel connection. In FTP Active mode, the FTP Client initiates the TCP three-way handshake and then connects to the FTP Server at TCP port number 21 ( FTP Control well-known port) where the FTP Server waits for the Control channel connection. FTP Active mode uses TCP port 20 for Data channel, but FTP Passive mode uses a random port number above 1023 (above well-known port range) for Data channel.įollowing sections explain how FTP Active mode and FTP Passive mode works and the differences between FTP Active mode and FTP Passive mode. Depending on the mode used, the port used for FTP Data connection is NOT always on TCP port 20. Misconception that FTP Data connection uses TCP port 20 always, which is not true. Two different modes of FTP are 1) Active mode and 2) Passive mode (PASV). There are 2 different modes for FTP, both works differently. Actual file transfer happens by creating FTP Data connection between FTP Client and FTP Server, after the user is authenticated over FTP control channel. FTP Server and FTP Client utilizes two different TCP ports, one is for FTP Control (also called as Command) connection and other is for FTP Data connection.īy default, FTP Server service (or daemon in Unix/Linux) listens exclusively on TCP port 21 for FTP Control channel connection. One is called as FTP Control (also called as Command) and other one is FTP Data. To make file transfer happen, FTP (File Transfer Protocol) creates two different connection channels between FTP Server and FTP Client. FTP uses TCP as its Layer 4 ( Transport Layer) protocol. Ports used by FTP (File Transfer Protocol)įTP is not similar to other protocols of TCP/IP protocol suite. You need an FTP Server software and FTP Client software for file transfer. Similar to other protocols in TCP/IP protocol suite, FTP (File Transfer Protocol) also has a Client/Server style of operation. FTP (File Transfer Protocol) is used to transfer electronic files from one computer to another computer. First RFC for FTP was published in the year 1971. As we had learned in previous lessons, FTP (File Transfer Protocol) is one among the early protocols of TCP/IP protocol suite. If you are experiencing any issues, please try another FTP client software or, alternatively, use SFTP (FTP over SSH).FTP (File Transfer Protocol) is a protocol belongs to the Application Layer of the TCP/IP protocol suite. For this example, use 5000 - 5010 as the local port range, and 5000 as the remote port.ĭue to environmental factors and slight differences with the implementation of this feature in different FTP clients and server software, it is possible Passive Mode may be unavailable. For FTP, use the same local ports that are configured on the remote host. One for the ports used for data connections.One for port 21 that covers any port on the local computer as well as port 21 on the remote machine.For example, if an FTP server uses port 21 for control and then 5000 to 5010 for data connections, add two forwards: Set each port manually on the Take Control console, or use a port range.
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