The following table lists commonly used ECS instance ports.

Port Service Description
21 FTP A port opened by the FTP service is used for uploading and downloading files.
22 SSH An SSH port is used to connect to a Linux instance by using a password in command-line mode.
23 Telnet The Telnet port is used for Telnet to log on to the ECS instance.
25 SMTP The port that is open to the SMTP service is used for sending mails.

Based on security concerns, ECS instance Port 25 is restricted by default. See apply to open TCP port 25to remove the limit.

80 HTTP Provides access to HTTP services, such as IIS, Apache, and Nginx.

We recommend that you verify if TCP port 80 works properly .

110 POP3 A port used for the POP3 protocol, which is a protocol for sending and receiving emails.
143 IMAP A port used for IMAP (Internet Message Access Protocol), which is a protocol for receiving emails.
443 HTTPS A port used to provide access to the HTTPS service. HTTPS is a protocol that provides encryption and transmission through secure ports.
1433 SQL Server The TCP port of the SQL Server that is used for external service by SQL Server.
1434 SQL Server The SQL Server UDP port that is used to return which TCP/IP port SQL Server uses.
1521 Oracle An Oracle communications port. The port that needs to be released by Oracle SQL is deployed on the ECS instance.
3306 MySQL The port through which the MySQL database provides external service.
3389 Windows Server Remote Desktop Services The Windows Server Remote Desktop Services port can be used to connect to a Windows instance.
8080 Proxy port Similar to 80 port, port 8080 is used by WWW agents to enable web browsing. If you are using port 8080, when you visit a Web site or use a proxy server, you must add :8080 after the IP Address: 8080. If you install the Apache Tomcat service, the default service port is 8080.
137, 138, 139 NetBIOS protocol
  • Ports 137 and 138 are UDP ports that are used to transfer files through the network neighbor.
  • The connection entering through the port 139 attempts to obtain the NetBIOS/smb service.
NetBIOS protocols are often used for Windows files, printer sharing, and samba.

Some ports cannot be accessed

Issue: An ECS instance attempts to listen for the corresponding port, but the port is not accessible, while other ports can be accessed normally.

Cause: Some operators determine that port numbers 135, 139, 444, 445, 5800, 5900, and related ports, are high-risk ports, which are then blocked by default.

Resolution: We recommend that you change the port to another port number

Related topic

For more information on how to release a service port through a security group, see add security group rules.