Open Internet or Unix domain socket connection

# stream_socket_client

(PHP 5, PHP 7, PHP 8)

stream_socket_client — Open Internet or Unix domain socket connection

### Description

stream_socket_client(
string `$address`,
int `&$error_code` = `null`,
string `&$error_message` = `null`,
?float `$timeout` = `null`,
int `$flags` = `STREAM_CLIENT_CONNECT`,
?resource `$context` = `null`
): resource|false

Initiates a stream or datagram connection to the destination specified by `address`. The type of socket created is determined by the transport specified using standard URL formatting: `transport://target`. For Internet Domain sockets (AF_INET) such as TCP and UDP, the `target` portion of the `address` parameter should consist of a hostname or IP address followed by a colon and a port number. For Unix domain sockets, the `target` portion should point to the socket file on the filesystem.

> Note:

> The stream will by default be opened in blocking mode. You can switch it to non-blocking mode by using stream_set_blocking().

### Parameters

`address`

  Address to the socket to connect to.

`error_code`

  Will be set to the system level error number if connection fails.

`error_message`

  Will be set to the system level error message if the connection fails.

`timeout`

  Number of seconds until the `connect()` system call should timeout. By default, default_socket_timeout is used.

  > Note: This parameter only applies when not making asynchronous connection attempts.

  > Note:

  > To set a timeout for reading/writing data over the socket, use the stream_set_timeout(), as the `timeout` only applies while making connecting the socket.

`flags`

  Bitmask field which may be set to any combination of connection flags. Currently the select of connection flags is limited to `STREAM_CLIENT_CONNECT` (default), `STREAM_CLIENT_ASYNC_CONNECT` and `STREAM_CLIENT_PERSISTENT`.

`context`

  A valid context resource created with stream_context_create().

### Return Values

On success a stream resource is returned which may be used together with the other file functions (such as fgets(), fgetss(), fwrite(), fclose(), and feof()), `false` on failure.

### Errors/Exceptions

On failure the `error_code` and `error_message` arguments will be populated with the actual system level error that occurred in the system-level `connect()` call. If the value returned in `error_code` is `0` and the function returned `false`, it is an indication that the error occurred before the `connect()` call. This is most likely due to a problem initializing the socket. Note that the `error_code` and `error_message` arguments will always be passed by reference.

### Changelog

Version | Description
--- | ---
8.0.0 | `timeout` and `context` are now nullable.

### Examples

Example #1 stream_socket_client() example

`<?php
$fp = stream_socket_client("tcp://www.example.com:80", $errno, $errstr, 30);
if (!$fp) {
echo "$errstr ($errno)<br />\n";
} else {
fwrite($fp, "GET / HTTP/1.0\r\nHost: www.example.com\r\nAccept: */*\r\n\r\n");
while (!feof($fp)) {
echo fgets($fp, 1024);
}
fclose($fp);
}
?>`

Example #2 Using UDP connection

Retrieving the day and time from the UDP service "daytime" (port 13) on localhost.

`<?php
$fp = stream_socket_client("udp://127.0.0.1:13", $errno, $errstr);
if (!$fp) {
echo "ERROR: $errno - $errstr<br />\n";
} else {
fwrite($fp, "\n");
echo fread($fp, 26);
fclose($fp);
}
?>`

### Notes

Warning

UDP sockets will sometimes appear to have opened without an error, even if the remote host is unreachable. The error will only become apparent when you read or write data to/from the socket. The reason for this is because UDP is a "connectionless" protocol, which means that the operating system does not try to establish a link for the socket until it actually needs to send or receive data.

> Note: When specifying a numerical IPv6 address (e.g. `fe80::1`), you must enclose the IP in square brackets—for example, `tcp://[fe80::1]:80`.

> Note:

> Depending on the environment, the Unix domain or the optional connect timeout may not be available. A list of available transports can be retrieved using stream_get_transports(). See List of Supported Socket Transports for a list of built in transports.

### See Also

- stream_socket_server() - Create an Internet or Unix domain server socket
- stream_set_blocking() - Set blocking/non-blocking mode on a stream
- stream_set_timeout() - Set timeout period on a stream
- stream_select() - Runs the equivalent of the select() system call on the given arrays of streams with a timeout specified by seconds and microseconds
- fgets() - Gets line from file pointer
- fgetss() - Gets line from file pointer and strip HTML tags
- fwrite() - Binary-safe file write
- fclose() - Closes an open file pointer
- feof() - Tests for end-of-file on a file pointer
- cURL Functions

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