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gethostbyaddr
Network Functions
PHP Manual

# fsockopen

(PHP 4, PHP 5)

fsockopen — Open Internet or Unix domain socket connection

### Description

resource fsockopen ( string `$hostname` [, int `$port` = -1 [, int `&$errno` [, string `&$errstr` [, float `$timeout` = ini_get("default_socket_timeout") ]]]] )

Initiates a socket connection to the resource specified by `hostname`.

PHP supports targets in the Internet and Unix domains as described in List of Supported Socket Transports. A list of supported transports can also be retrieved using stream_get_transports().

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

The function stream_socket_client() is similar but provides a richer set of options, including non-blocking connection and the ability to provide a stream context.

### Parameters

`hostname`

  If OpenSSL support is installed, you may prefix the `hostname` with either ssl:// or tls:// to use an SSL or TLS client connection over TCP/IP to connect to the remote host.

`port`

  The port number. This can be omitted and skipped with -1 for transports that do not use ports, such as unix://.

`errno`

  If provided, holds the system level error number that occurred in the system-level connect() call.

  If the value returned in `errno` 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.

`errstr`

  The error message as a string.

`timeout`

  The connection timeout, in seconds.

  > Note:

  > If you need to set a timeout for reading/writing data over the socket, use stream_set_timeout(), as the `timeout` parameter to fsockopen() only applies while connecting the socket.

### Return Values

fsockopen() returns a file pointer which may be used together with the other file functions (such as fgets(), fgetss(), fwrite(), fclose(), and feof()). If the call fails, it will return `FALSE`

### Errors/Exceptions

Throws `E_WARNING` if `hostname` is not a valid domain.

### Changelog

Version | Description
--- | ---
4.3.0 | Added support for the `timeout` parameter on win32.
4.3.0 | SSL and TLS over TCP/IP support was added.

### Examples

Example #1 fsockopen() Example

`<?php
$fp = fsockopen("www.example.com", 80, $errno, $errstr, 30);
if (!$fp) {
echo "$errstr ($errno)<br />\n";
} else {
$out = "GET / HTTP/1.1\r\n";
$out .= "Host: www.example.com\r\n";
$out .= "Connection: Close\r\n\r\n";
fwrite($fp, $out);
while (!feof($fp)) {
echo fgets($fp, 128);
}
fclose($fp);
}
?>`

Example #2 Using UDP connection

The example below shows how to retrieve the day and time from the UDP service "daytime" (port 13) in your own machine.

`<?php
$fp = fsockopen("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

> Note:

> Depending on the environment, the Unix domain or the optional connect timeout may not be available.

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.

### See Also

- pfsockopen() - Open persistent Internet or Unix domain socket connection
- stream_socket_client() - Open Internet or Unix domain socket connection
- stream_set_blocking() - Set blocking/non-blocking mode on a stream
- stream_set_timeout() - Set timeout period on a stream
- 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
- socket_connect() - Initiates a connection on a socket
- The Curl extension

dns_get_record
gethostbyaddr
Network Functions
PHP Manual