A Network socket or net socket is a socket for the Internet protocol suite (TCP and UPD) that creates a network connection to or from which information is transmitted in the network between a server (local machine) and a client (remote machine).
This connection is implemented by software (not hardware) by creating a network interface.
Socket communications are nowadays bidirectional (full duplex) (With Tcp sure, udp ???)
A net socket on an operating system level is characterized by a unique combination of the following:
- Local socket address
- Protocol: A transport protocol (e.g., TCP, UDP, raw IP, or others). TCP port 53 and UDP port 53 are consequently different, distinct sockets.
A socket address is the combination of
There are several Internet socket types available:
- Datagram sockets, also known as connectionless sockets
- Stream sockets, also known as connection-oriented sockets, which use Transmission Control Protocol (TCP) or Stream Control Transmission Protocol (SCTP).
- Raw sockets (or Raw IP sockets), typically available in routers and other network equipment. Here the transport layer is bypassed, and the packet headers are made accessible to the application.
- Listening: Computer processes that provide application services are called as servers, and create sockets on start up that are in listening state. These sockets are waiting for initiatives from client programs. See TCP Listening state
The operating system forwards the payload of incoming IP packets to the corresponding application by extracting the socket address information from the IP and transport protocol headers and stripping the headers from the application data.
The output of netstat showing a socket Id with its state
- Number of open sockets with netstat
netstat | grep port
- port is the listening port.
Netcat can be used to send data over socket.
SocketAddress bindAddress = SocketAddress.inetSocketAddress(4043, "localhost");
For IPC, you could also use ObjectOutputStream and ObjectInputStream connected to network sockets and exchange Java objects directly between the two programs. Or you could design your own protocol.