Once I have identified endpoints within our network, the next step is to perform a port scan. Computers that support communication protocols utilize ports in order to make connections. In order to support different conversations with multiple applications, ports are used to distinguish various communications in the same machine or server. For example, web servers can use the Hypertext Transfer Protocol (HTTP) to provide access to a web page which utilizes TCP port number 80 by default. The Simple Mail Transfer Protocol or SMTP uses port 25 to send or transmit mail messages. For each unique IP address, a protocol port number is identified by a 16-bit number, commonly known as the port number 0-65,535. The combination of a port number and IP address provides a complete address for communication. Depending on the direction of the communication, both a source and destination address (IP address and port combination) are required.