# PR_NewTCPSocket

Creates a new IPv4 TCP socket.

## Syntax

```{code}
#include <prio.h>

PRFileDesc* PR_NewTCPSocket(void);
```

### Returns

The function returns one of the following values:

- Upon successful completion, a pointer to the {ref}`PRFileDesc` object
  created for the newly opened IPv4 TCP socket.
- If the creation of a new TCP socket failed, `NULL`.

## Description

TCP (Transmission Control Protocol) is a connection-oriented, reliable
byte-stream protocol of the TCP/IP protocol suite. {ref}`PR_NewTCPSocket`
creates a new IPv4 TCP socket. A TCP connection is established by a
passive socket (the server) accepting a connection setup request from an
active socket (the client). Typically, the server binds its socket to a
well-known port with {ref}`PR_Bind`, calls {ref}`PR_Listen` to start listening
for connection setup requests, and calls {ref}`PR_Accept` to accept a
connection. The client makes a connection request using {ref}`PR_Connect`.

After a connection is established, the client and server may send and
receive data between each other. To receive data, one can call
{ref}`PR_Read` or {ref}`PR_Recv`. To send data, one can call {ref}`PR_Write`,
{ref}`PR_Writev`, {ref}`PR_Send`, or {ref}`PR_TransmitFile`. {ref}`PR_AcceptRead` is
suitable for use by the server to accept a new client connection and
read the client's first request in one function call.

A TCP connection can be shut down by {ref}`PR_Shutdown`, and the sockets
should be closed by {ref}`PR_Close`.

## See Also

{ref}`PR_NewTCPSocket` is deprecated because it is hardcoded to create an
IPv4 TCP socket. New code should use {ref}`PR_OpenTCPSocket` instead, which
allows the address family (IPv4 or IPv6) of the new TCP socket to be
specified.