For other uses, see RF (disambiguation) . Radio frequency (RF): any of the electromagnetic wave frequencies that lie in the range extending from around 7003300000000000000â 3 kHz to 7011300000000000000â 300 GHz, which include those frequencies used for communications or radar signals.owever, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune into a particular frequency (or frequency range). This is typically done via a resonator â in its simplest form, a circuit with a capacitor and an inductor form a tuned circuit.
How the TCP Port 21 Works With FTP. The File Transfer Protocol Uses Port 20 and 21. The File Transfer Protocol (FTP) provides a means to transfer information online, much like how the Hypertext Transfer Protocol (HTTP) is used through a web browser. FTP, however, operates on two different TCP ports: 20 and 21.
The end-users will access this file server via FTP to start copying the files to their local folder/system. FTP requires a TCP/IP network to function, and relies on the use of one or more FTP clients. The FTP client acts as the communication agent to interact with the server to download or upload files. In other words, the FTP client sends out connections to the FTP server. Upon listening to the request from the client to either upload or download a file, the FTP server performs the file transfer operation.