Because there are too many services, there are also many corresponding ports. Here, we only briefly describe some commonly used services and corresponding ports, and arrange the order in ascending order, each item starts with "port type: port number" (for example, "TCP: 10000 ").
- TCP20: used for FTP data transmission. For the FTP transmission mode in active mode (PORT), see the illustration of FTP active mode and passive mode and client settings, the FTP server uses the TCP20 port to actively connect to the client for data transmission.
- TCP21: used for FTP message control. In the FTP service, when the client uses a passive method (PASV) to connect to the FTP server, it first connects to port TCP21 of the server for negotiation, the contents of the negotiation include the port opened by the server for data transmission. If the client uses the active mode, the client will tell the server which port it opens and wait for the FTP server to connect to the port TCP20 for data transmission.
- TCP22: used for SSH (Secure Shell) connections. SSH connections are much safer than telnet-based plaintext data transmission. By default, the TCP22 port is opened for remote management of the system.
- TCP23: the port used by TELNET. In a windows command prompt, use "telnet + Server IP + port" to access the port corresponding to the remote host, for example, after telnet pop.qq.com port 110, you can enter the corresponding command to operate emails in the mailbox. This command is often used to test whether the host opens the corresponding port. If the host does not open a meeting, the system prompts that the connection fails.
- TCP25: used for SMTP services, that is, for sending mails. Both client-side mails and server-forwarded mails send data to the TCP25 port of the remote host.
- UDP53: the DNS Server opens this port to provide domain name resolution services for the client.
- TCP80: You don't need to introduce it. You can use other custom ports to provide WEB services. For example, in IIS, you can set different ports to differentiate different sites, but you need to add this port at the back end during access.
- TCP110: used for POP3 services. Generally, outlook and foxmail are used to connect to the port TCP110 of the mail server to receive emails.
- TCP135: used for Remote Procedure Call (RPC). You can find Remote Procedure Call (RPC) in the service list and view its dependency. You can see that N services depend on this service, the importance can be imagined.
- TCP139: used for windows File Sharing and printer sharing. When copying shared files, the local random port is connected to the peer's TCP139 port to transmit data.
- TCP143: Used for the IMAP service. IMAP is used to receive emails. Compared with POP3, IMAP provides more functions.
- TCP389: the port of the LADP protocol (simple Directory Access Protocol). The windows Domain environment is based on the ldap protocol architecture, and all user information is stored in the Active Directory, the application can connect to the TCP389 port of the server to obtain user information. For example, the mail software can connect to the Active Directory to obtain the list of emails saved in the Active Directory.
- TCP443: used for HTTPS (encrypted HTTP connection), which is widely used. For example, the HTTPS connection provided when you use online banking to query bank account information.
- TCP995: used for encrypted POP3 connections. When setting a GMAIL mailbox on the mail client, you must check "this server requires encrypted connection (SSL)" after the receiving server (POP3 )", then the port is automatically changed to 995, as shown in:
- Port TCP3389: used for Remote Desktop Connection. In windwos xp, to enable Remote Desktop Services, right-click my computer, select properties, and switch to Remote options, then, select allow remote connection to the computer under the Remote Desktop. By default, the system administrator has the permission to log on remotely, as shown in:
All of the above are commonly used ports. In fact, many default ports can be changed. For example, port 80 on the WEB can be modified in IIS or APACHE; 3389 in the Remote Desktop Connection can be modified in the registry, and the system restart takes effect.
