TCPSocket

TCP socket is an API endpoint for network communication that uses the Transmission Control Protocol (TCP). A TCP socket is identified by a local IP address and port, and by the remote endpoint after a connection is established. Applications typically create a socket with an address family of AF_INET or AF_INET6 and a socket type of SOCK_STREAM.

In practice, a server creates a passive listener by binding to a local address and port, then calling listen and accept to obtain a connected socket for each client. A client creates an active connection by calling connect to a server’s address. The result is a bidirectional, connected socket that provides a byte stream. Data is delivered as a continuous flow; the application must implement its own framing if message boundaries matter.

TCP provides reliable, in-order delivery with error detection, acknowledgments, and retransmission. It also implements flow control and congestion control, and maintains state for each connection. Ports allow multiplexing multiple connections on a single host, and the protocol is connection-oriented, meaning a separate connection is established for each communicating pair.

Sockets can operate in blocking or non-blocking modes and are usable in synchronous or asynchronous I/O models. They are available across programming languages and platforms, often via BSD sockets or platform-specific wrappers (for example, Windows Winsock). Security can be added by layering TLS/SSL over the TCP connection.

Common considerations include performance tuning (such as Nagle’s algorithm and buffering), handling partial reads or writes, timeouts, and dealing with network issues like NAT and firewalls. TCP sockets are widely used for protocols such as HTTP, SMTP, and SSH due to their reliability and ordered delivery.