src/main/java/com/alipay/remoting/rpc/RpcClient.java
public boolean checkConnection(String addr) {
        Url url = this.addressParser.parse(addr);
        Connection conn = this.connectionManager.get(url.getUniqueKey());
        try {
            this.connectionManager.check(conn);
        } catch (Exception e) {
            return false;
        }
        return true;
    }
public boolean checkConnection(String addr) {
        Url url = this.addressParser.parse(addr);
        Connection conn = this.connectionManager.get(url.getUniqueKey());
        try {
            this.connectionManager.check(conn);
        } catch (Exception e) {
            return false;
        }
        return true;
    }
check connection, the address format example - 127.0.0.1:12200?key1=value1&key2=value2

@param addr
@throws RemotingException
@return true if and only if there is a connection, and the connection is active and writable;else return false