https://www.tutorialspoint.com/java/java_networking.htm

[ Java – Networking ]

• The term network programming refers to writing programs that execute across multiple devices (computers), in which the devices are all connected to each other using a network.

• The java.net package provides support for the two common network protocols −

  • TCP  − TCP stands for Transmission Control Protocol, which allows for reliable communication between two applications. TCP is typically used over the Internet Protocol, which is referred to as TCP/IP.
  • UDP  − UDP stands for User Datagram Protocol, a connection-less protocol that allows for packets of data to be transmitted between applications.

• cmd 명령어

: netstat -an ⇒ 몇 번 포트가 사용 중에 있는지 확인 가능