code: func replconfCommand(c *client) error {
  	args := c.args
  	if len(args)%2 != 0 {
  		return ErrCmdParams
  	}
  
  	if !c.app.ldb.ReplicationUsed() {
  		return ledis.ErrRplNotSupport
  	}
  
  	//now only support "listening-port"
  	for i := 0; i < len(args); i += 2 {
  		switch strings.ToLower(hack.String(args[i])) {
  		case "listening-port":
  			var host string
  			var err error
  			if _, err = num.ParseUint16(hack.String(args[i+1])); err != nil {
  				return err
  			}
  			if host, _, err = net.SplitHostPort(c.remoteAddr); err != nil {
  				return err
  			} else {
  				c.slaveListeningAddr = net.JoinHostPort(host, hack.String(args[i+1]))
  			}
  
  			c.app.addSlave(c)
  		default:
  			return ErrSyntax
  		}
  	}
  
  	c.resp.writeStatus(OK)
  	return nil
  }
docs: //inner command, only for replication
  //REPLCONF <option> <value> <option> <value> ...