You can use nginx’s limit_conn_module to limit the number of client IP connections.
The following is a simplified configuration:

http { limit_conn_zone $binary_remote_addr zone=addr:10m; server { limit_conn addr 1; } }

• limit_conn_zoneDefine a bucket that limits connections;

• $binary_remote_addrmeans to calculate the number of connections based on the client IP as the key;

• zone=addrDeclare the name of this bucket;

• limit_connexecutes a limit on the number of connections, and the followingaddris to call the previously configured bucket.