Port 465 - SMTPS (SMTP Secure): Provides secure email sending. Port 443 - HTTPS (Hypertext Transfer Protocol Secure): Used for secure web browsing. Port 143 - IMAP (Internet Message Access Protocol): Manages email on a remote mail server. Port 110 - POP3 (Post Office Protocol version 3): Retrieves email from a server. Port 80 - HTTP (Hypertext Transfer Protocol): Used for unencrypted web browsing. Port 53 - DNS (Domain Name System): Resolves domain names to IP addresses. Port 25 - SMTP (Simple Mail Transfer Protocol): Handles outgoing email. Port 23 - Telnet: Used for unencrypted remote terminal access. Port 22 - SSH (Secure Shell): Provides secure remote login and file transfer capabilities. Port 21 - FTP (File Transfer Protocol): Used for transferring files over a network. They are selected dynamically by the client and can change with each new connection. They are assigned by the Internet Assigned Numbers Authority (IANA) to prevent conflicts.ĭynamic or Private Ports (49152-65535): Also known as ephemeral ports, these are used for temporary purposes by client applications when making connections to servers. Registered Ports (1024-49151): These ports can be used by user applications and services but are often reserved for specific applications or protocols. Port numbers in this range are typically associated with well-known services like HTTP (Port 80), FTP (Port 21), and SSH (Port 22). UDP is just shouting at the other computer without any verification if the message ever arrives.Well-Known Ports (0-1023): These are reserved for system services and common applications. Protocols that run over UDP (rather than TCP) are similar, except no connection is established. A bidirectional TCP connection is established and communication follows according to the FTP protocol.Īgain, the active mode is a bit more complicated and I'm not familiar with it enough to explain it. Client opens a randomly selected ephemeral port and tries to connect to the server. Server opens a known port (typically 21) and listens for connections. In passive mode it works like the SMTP example I've explained at the beginning. in the same sense, how is port 21(ftp) used? every time there's a process that uses ftp, this and only this port is used? I won't go into details about the FTP example because 1) I want to keep this answer focused on the networking part and 2) while FTP's passive mode is rather simple, there's also the active mode which I'm not familiar with. What is being sent and how is determined by the protocol. You can use then both for sending and receiving (and client's sending is server's receiving). maybe I got this wrong, but ports are used both as if I am the sender(e.g: I want to make an ssh connection to another pc, so I would send this connection through my port 22 to the others pc port 22), or ports are only for receiving said information, that's to say port 21 receives ftp info but doesn't necessarily transfer files through that port? Maybe they're using a different approach. The server may be internally making a SMTP connection to the outgoing mail server, but we don't know that. You don't send an email - you instruct the server to do it in your name. You're only talking with some HTTP(S) servers. If you're using Gmail through its HTTPS web interface in a browser, then you're connecting to it on port 443 only. For example if you go to gmail(port 443 for https) and you send an email using the stmp, is this port 25 being used somehow? You can make multiple client connections simultaneously.You can make client connections if the port 25 is already taken by a server.It's the client that's connecting to the server - it's enough for client to know server's port, then it can tell the server which port on the client it should talk to. That's because it's not necessary to use a known port number on client. The client is actually using a randomly selected ephemeral port. But we've all agreed that 25 is the default server port for convenience. You can use any other port if both the server and client are configured to use it. SMTP usually runs on port 25 on the server. Now port 25 is called stmp for that matter
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