You can create a TCP listener for a Cloud Load Balancer (CLB) instance to forward TCP requests from the client. TCP is suitable for scenarios that have high requirements for reliability and data accuracy but relatively low requirements for transmission speed, such as file transfer, email messaging, and remote login. Real servers bound to the TCP listener can directly obtain the real client IP address.
1. Log in to the CLB console and click Instance management in the left sidebar.
2. Select your region in the top-left corner of the CLB instance list and click Configure listener in the Operation column of the target instance.
3. Under TCP/UDP/TCP SSL/QUIC listener, click Create and configure the TCP listener in the pop-up window.
3.1 Configure basic parameters
Parameter
Description
Example
Name
Listener name.
test-tcp-80
Listening protocol and port
Listening protocol: In this case, select TCP.
Listening port: The port used to receive requests and forward them to the real server. The port number ranges from 1 to 65535.
A listening port must be unique in the same CLB instance.
TCP:80
Balancing method
CLB supports two scheduling algorithms for TCP listeners: weighted round robin (WRR) and weighted least connections (WLC).
WRR: Requests are distributed to real servers in sequence based on their weights. This algorithm performs scheduling based on the number of new connections. Servers with higher weights are more likely to be scheduled and servers with the same weight process the same number of connections.
WLC: Loads of servers are estimated based on the number of active connections to the servers. This algorithm performs scheduling based on server loads and weights. For servers with the same weight, those have less loads are more likely to be scheduled.
Note: If WLC is selected, the listener does not support session persistence.
WRR
Two-way RST
If this option is selected, corresponding operations will send RST packets to both ends (client and server) to close the connection; otherwise, two-way RST packets will not be sent, and the persistent connection will exist until it times out.
Selected
3.2 Configure health check
For more information about health check, see TCP Listener.
3.3 Configure session persistence
Parameter
Description
Example
Session persistence
After session persistence is enabled, a CLB listener will distribute access requests from the same client to the same real server.
TCP session persistence is implemented based on the client IP address. The access requests from the same IP address are forwarded to the same real server.
Session persistence can be enabled for WRR scheduling but not WLC scheduling.
Enabled
Hold Time
Session persistence duration.
Session persistence is terminated if there are no new requests in the connection within the specified duration.
Value range: 30-3600 seconds
30 seconds
Step 2. Bind a real server
1. On the Listener management page, click the created listener TCP:80 to view the bound real servers on the right of the listener.
2. Click Bind, select the target real server, and configure the server port and weight in the pop-up window.
Note:
If you set Default port first and then select real servers, the port of every real server is the default port.
Step 3. Configure a security group (optional)
You can configure a CLB security group to isolate public network traffic. For more information, see Configuring a CLB Security Group.
Step 4. Modify or delete a listener (optional)
If you need to modify or delete a created listener, click the listener on the Listener management page and click
Yes
No
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