# xpc_session_t A C type that sends messages to a server process. ``` typealias xpc_session_t = OS_xpc_session ``` ## Discussion XPC sessions are stateful connections you use to send structured messages to a separate process. Once established, a session remains active until one side of the connection cancels it, at which point the system invalidates the connection. Unlike lower-level `xpc_connection` functions, the system makes no attempt to reestablish a connection or relaunch the service. ## Topics ### Creating a session [`typealias xpc_session_t`](/documentation/XPC/xpc_session_t-49tiv) [`func xpc_session_create_mach_service(UnsafePointer, dispatch_queue_t?, xpc_session_create_flags_t, AutoreleasingUnsafeMutablePointer?) -> (any OS_xpc_object)?`](/documentation/XPC/xpc_session_create_mach_service(_:_:_:_:)) [`func xpc_session_create_xpc_service(UnsafePointer, dispatch_queue_t?, xpc_session_create_flags_t, AutoreleasingUnsafeMutablePointer?) -> (any OS_xpc_object)?`](/documentation/XPC/xpc_session_create_xpc_service(_:_:_:_:)) [`struct xpc_session_create_flags_t`](/documentation/XPC/xpc_session_create_flags_t-swift.struct) [`func xpc_session_copy_description(any OS_xpc_object) -> UnsafeMutablePointer?`](/documentation/XPC/xpc_session_copy_description(_:)) [`func xpc_session_set_target_queue(any OS_xpc_object, dispatch_queue_t?)`](/documentation/XPC/xpc_session_set_target_queue(_:_:)) [`extern xpc_session_txpc_session_create_xpc_service(const char *name, dispatch_queue_t target_queue, xpc_session_create_flags_t flags, xpc_rich_error_t*error_out);`](/documentation/XPC/xpc_session_create_xpc_service) Establishes a connection to an XPC service with the name you specify. [`extern xpc_session_txpc_session_create_mach_service(const char *mach_service, dispatch_queue_t target_queue, xpc_session_create_flags_t flags, xpc_rich_error_t*error_out);`](/documentation/XPC/xpc_session_create_mach_service) Establishes a connection to a launch agent or launch daemon with the name you specify. [`typedef enum { ... } xpc_session_create_flags_t;`](/documentation/XPC/xpc_session_create_flags_t-c.enum) Options that specify how to create inactive or privileged sessions. [`extern void xpc_session_set_target_queue(xpc_session_t session, dispatch_queue_t target_queue);`](/documentation/XPC/xpc_session_set_target_queue) Sets the target dispatch queue on an inactive session for processing messages. [`extern char *xpc_session_copy_description(xpc_session_t session);`](/documentation/XPC/xpc_session_copy_description) Copies the description string of a session. ### Managing life cycle [`func xpc_session_activate(any OS_xpc_object, AutoreleasingUnsafeMutablePointer?) -> Bool`](/documentation/XPC/xpc_session_activate(_:_:)) [`func xpc_session_cancel(any OS_xpc_object)`](/documentation/XPC/xpc_session_cancel(_:)) [`func xpc_session_set_cancel_handler(any OS_xpc_object, xpc_session_cancel_handler_t)`](/documentation/XPC/xpc_session_set_cancel_handler(_:_:)) [`func xpc_session_set_incoming_message_handler(any OS_xpc_object, xpc_session_incoming_message_handler_t)`](/documentation/XPC/xpc_session_set_incoming_message_handler(_:_:)) Sets a handler to receive incoming messages for a session. [`typealias xpc_session_incoming_message_handler_t`](/documentation/XPC/xpc_session_incoming_message_handler_t-elj) [`extern bool xpc_session_activate(xpc_session_t session, xpc_rich_error_t*error_out);`](/documentation/XPC/xpc_session_activate) Activates a session so you can send messages. [`extern void xpc_session_set_incoming_message_handler(xpc_session_t session, xpc_session_incoming_message_handler_t handler);`](/documentation/XPC/xpc_session_set_incoming_message_handler) Sets a handler to receive incoming messages for a session. [`typedef void (^)(NSObject *) xpc_session_incoming_message_handler_t;`](/documentation/XPC/xpc_session_incoming_message_handler_t-3eb2a) A closure that receives an incoming message for a session. [`extern void xpc_session_cancel(xpc_session_t session);`](/documentation/XPC/xpc_session_cancel) Cancels a session, discarding any unsent messages. [`extern void xpc_session_set_cancel_handler(xpc_session_t session, xpc_session_cancel_handler_t cancel_handler);`](/documentation/XPC/xpc_session_set_cancel_handler) Sets a handler the session calls when it’s canceled. [`typedef void (^)(NSObject *) xpc_session_cancel_handler_t;`](/documentation/XPC/xpc_session_cancel_handler_t-7y2lv) A block the session calls when it’s canceled. [`typealias xpc_session_cancel_handler_t`](/documentation/XPC/xpc_session_cancel_handler_t-65b6f) ### Sending messages [`extern xpc_rich_error_txpc_session_send_message(xpc_session_t session, xpc_object_t message);`](/documentation/XPC/xpc_session_send_message) Sends a message over the session to the destination service. [`extern void xpc_session_send_message_with_reply_async(xpc_session_t session, xpc_object_t message, xpc_session_reply_handler_t reply_handler);`](/documentation/XPC/xpc_session_send_message_with_reply_async) Sends a message asynchronously over the session to the destination service, calling a handler after receiving a reply. [`typedef void (^)(NSObject *, NSObject *) xpc_session_reply_handler_t;`](/documentation/XPC/xpc_session_reply_handler_t-7kfe4) A block that receives the reply to a message a session sends. [`extern xpc_object_txpc_session_send_message_with_reply_sync(xpc_session_t session, xpc_object_t message, xpc_rich_error_t*error_out);`](/documentation/XPC/xpc_session_send_message_with_reply_sync) Sends a message over the session to the destination service, blocking the caller until receiving a reply. [`typealias xpc_rich_error_t`](/documentation/XPC/xpc_rich_error_t) A type that describes an error, and whether you can retry the operation that experienced the error. [`func xpc_rich_error_can_retry(xpc_rich_error_t) -> Bool`](/documentation/XPC/xpc_rich_error_can_retry(_:)) Returns a Boolean that indicates whether you can retry the operation that experienced an error. [`func xpc_rich_error_copy_description(xpc_rich_error_t) -> UnsafeMutablePointer?`](/documentation/XPC/xpc_rich_error_copy_description(_:)) Copies the string description of an error. [`func xpc_session_send_message(any OS_xpc_object, xpc_object_t) -> xpc_rich_error_t?`](/documentation/XPC/xpc_session_send_message(_:_:)) [`func xpc_session_send_message_with_reply_async(any OS_xpc_object, xpc_object_t, xpc_session_reply_handler_t)`](/documentation/XPC/xpc_session_send_message_with_reply_async(_:_:_:)) [`typealias xpc_session_reply_handler_t`](/documentation/XPC/xpc_session_reply_handler_t-2hf7c) [`func xpc_session_send_message_with_reply_sync(any OS_xpc_object, xpc_object_t, AutoreleasingUnsafeMutablePointer?) -> xpc_object_t?`](/documentation/XPC/xpc_session_send_message_with_reply_sync(_:_:_:)) ### Working with code signing [`func xpc_session_set_peer_code_signing_requirement(xpc_session_t, UnsafePointer) -> Int32`](/documentation/XPC/xpc_session_set_peer_code_signing_requirement(_:_:)) --- Copyright © 2026 Apple Inc. 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