connection.h File Reference

MPD client library. More...

#include "protocol.h"
#include "error.h"
#include "compiler.h"
#include <stdbool.h>

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Functions
struct mpd_connection *	mpd_connection_new (const char *host, unsigned port, unsigned timeout_ms)
struct mpd_connection *	mpd_connection_new_async (struct mpd_async *async, const char *welcome)
void	mpd_connection_free (struct mpd_connection *connection)
const struct mpd_settings *	mpd_connection_get_settings (const struct mpd_connection *connection)
bool	mpd_connection_set_keepalive (struct mpd_connection *connection, bool keepalive)
void	mpd_connection_set_timeout (struct mpd_connection *connection, unsigned timeout_ms)
int	mpd_connection_get_fd (const struct mpd_connection *connection)
struct mpd_async *	mpd_connection_get_async (struct mpd_connection *connection)
enum mpd_error	mpd_connection_get_error (const struct mpd_connection *connection)
const char *	mpd_connection_get_error_message (const struct mpd_connection *connection)
enum mpd_server_error	mpd_connection_get_server_error (const struct mpd_connection *connection)
unsigned	mpd_connection_get_server_error_location (const struct mpd_connection *connection)
int	mpd_connection_get_system_error (const struct mpd_connection *connection)
bool	mpd_connection_clear_error (struct mpd_connection *connection)
const unsigned *	mpd_connection_get_server_version (const struct mpd_connection *connection)
int	mpd_connection_cmp_server_version (const struct mpd_connection *connection, unsigned major, unsigned minor, unsigned patch)

Detailed Description

MPD client library.

Do not include this header directly. Use mpd/client.h instead.

Definition in file connection.h.

Function Documentation

mpd_connection_new()

struct mpd_connection * mpd_connection_new	(	const char *	host,
		unsigned	port,
		unsigned	timeout_ms
	)

Opens a new connection to a MPD server. Both the name server lookup and the connect() call are done synchronously. After this function has returned, you should check if the connection was successful with mpd_connection_get_error().

Parameters

host	the server's host name, IP address or Unix socket path. If the resolver returns more than one IP address for a host name, this functions tries all of them until one accepts the connection. NULL is allowed here, which will connect to the default host (using the MPD_HOST environment variable if present).
port	the TCP port to connect to, 0 for default port (using the MPD_PORT environment variable if present). If "host" is a Unix socket path, this parameter is ignored.
timeout_ms	the timeout in milliseconds, 0 for the default timeout (the environment variable MPD_TIMEOUT may specify a timeout in seconds); you may modify it later with mpd_connection_set_timeout()

Returns

a mpd_connection object (which may have failed to connect), or NULL on out-of-memory

Since

libmpdclient 2.3 added support for MPD_HOST, MPD_PORT and MPD_TIMEOUT.

mpd_connection_new_async()

struct mpd_connection * mpd_connection_new_async	(	struct mpd_async *	async,
		const char *	welcome
	)

Creates a mpd_connection object based on an existing asynchronous MPD connection. You should not continue to use the mpd_async object. Note that mpd_connection_free() also frees your mpd_async object!

This function does not block at all, which is why you have to pass the welcome message to it.

Parameters

async	a mpd_async instance
welcome	the first line sent by MPD (the welcome message)

Returns

a mpd_connection object, or NULL on out-of-memory

mpd_connection_free()

void mpd_connection_free

(

struct mpd_connection *

connection

)

Close the connection and free all memory.

Parameters

connection

the connection to MPD

mpd_connection_get_settings()

const struct mpd_settings * mpd_connection_get_settings

(

const struct mpd_connection *

connection

)

Returns the settings which were used to connect to the server. May be NULL if the settings are not known.

Since

libmpdclient 2.4

mpd_connection_set_keepalive()

bool mpd_connection_set_keepalive	(	struct mpd_connection *	connection,
		bool	keepalive
	)

Enables (or disables) TCP keepalives.

Keepalives are enabled using the SO_KEEPALIVE socket option. They may be required for long-idled connections to persist on some networks that would otherwise terminate inactive TCP sessions.

The default value is false.

Parameters

connection	the connection to MPD
keepalive	whether TCP keepalives should be enabled

Returns

true on success, false if setsockopt failed

Since

libmpdclient 2.10

mpd_connection_set_timeout()

void mpd_connection_set_timeout	(	struct mpd_connection *	connection,
		unsigned	timeout_ms
	)

Sets the timeout for synchronous operations. If the MPD server does not send a response during this time span, the operation is aborted by libmpdclient.

The initial value is the one passed to mpd_connection_new(). If you have used mpd_connection_new_async(), then the default value is 30 seconds.

Parameters

connection	the connection to MPD
timeout_ms	the desired timeout in milliseconds; must not be 0

mpd_connection_get_fd()

int mpd_connection_get_fd

(

const struct mpd_connection *

connection

)

Returns the file descriptor which should be polled by the caller. Do not use the file descriptor for anything except polling! The file descriptor never changes during the lifetime of this mpd_connection object.

To integrate this library in a non-blocking event I/O loop, use this function to obtain the underlying socket descriptor and register it in the event loop. As soon as it becomes ready for reading, use this library's functions to receive responses from MPD. Example:

if (!mpd_send_idle(conn))
    return handle_error();
register_socket(mpd_connection_get_fd(conn));

And in the event callback:

enum mpd_idle events = mpd_recv_idle(conn);
// handle the events
// .. and then call mpd_send_idle() again to keep listening

mpd_connection_get_async()

struct mpd_async * mpd_connection_get_async

(

struct mpd_connection *

connection

)

Returns the underlying mpd_async object. This can be used to send commands asynchronously. During an asynchronous command, you must not use synchronous mpd_connection functions until the asynchronous response has been finished.

If an error occurs while using mpd_async, you must close the mpd_connection.

mpd_connection_get_error()

enum mpd_error mpd_connection_get_error

(

const struct mpd_connection *

connection

)

Returns the libmpdclient error code. MPD_ERROR_SUCCESS means no error occurred.

mpd_connection_get_error_message()

const char * mpd_connection_get_error_message

(

const struct mpd_connection *

connection

)

Returns the human-readable (English) libmpdclient error message. Calling this function is only valid if an error really occurred. Check with mpd_connection_get_error().

For MPD_ERROR_SERVER, the error message is encoded in UTF-8. MPD_ERROR_SYSTEM obtains its error message from the operating system, and thus the locale's character set (and probably language) is used. Keep that in mind when you print error messages.

mpd_connection_get_server_error()

enum mpd_server_error mpd_connection_get_server_error

(

const struct mpd_connection *

connection

)

Returns the error code returned from the server. Calling this function is only valid if mpd_connection_get_error() returned MPD_ERROR_SERVER.

mpd_connection_get_server_error_location()

unsigned mpd_connection_get_server_error_location

(

const struct mpd_connection *

connection

)

Returns the location of the server error, i.e. an index within the command list. Calling this function is only valid in a command list response, and if mpd_connection_get_error() returned MPD_ERROR_SERVER.

Since

libmpdclient 2.4

mpd_connection_get_system_error()

int mpd_connection_get_system_error

(

const struct mpd_connection *

connection

)

Returns the error code from the operating system; on most operating systems, this is the errno value. Calling this function is only valid if mpd_connection_get_error() returned MPD_ERROR_SYSTEM.

May be 0 if the operating system did not specify an error code.

mpd_connection_clear_error()

bool mpd_connection_clear_error

(

struct mpd_connection *

connection

)

Attempts to recover from an error condition. This function must be called after a non-fatal error before you can continue using this object.

Returns

true on success, false if the error is fatal and cannot be recovered

mpd_connection_get_server_version()

const unsigned * mpd_connection_get_server_version

(

const struct mpd_connection *

connection

)

Returns a three-tuple containing the major, minor and patch version of the MPD protocol.

mpd_connection_cmp_server_version()

int mpd_connection_cmp_server_version	(	const struct mpd_connection *	connection,
		unsigned	major,
		unsigned	minor,
		unsigned	patch
	)

Compares the MPD protocol version with the specified triple.

Returns

-1 if the server is older, 1 if it is newer, 0 if it is equal