Error No Buffer Space Available when Using Java, MyBatis and MySql

I’ve met a very weird error, that are not supposed to happen, when using MyBatis and MySql. Somehow my Windows OS is running out of ports, this is the complete stacktrace.

Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(Unknown Source)
    at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)]

I found out it happened because im using traditional unpooled connection, changing it into pooled connection in MyBatis solved it.

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost/xxxx"/>
                <property name="username" value="xxxx"/>
                <property name="password" value=""/>
                <property name="poolMaximumActiveConnections" value="20"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>

    </mappers>
</configuration>