---
title: "init(serviceType:discoveryInfo:session:)"
framework: multipeerconnectivity
role: symbol
role_heading: Initializer
path: "multipeerconnectivity/mcadvertiserassistant/init(servicetype:discoveryinfo:session:)"
---

# init(serviceType:discoveryInfo:session:)

Initializes an advertiser assistant object.

## Declaration

```swift
init(serviceType: String, discoveryInfo info: [String : String]?, session: MCSession)
```

## Parameters

- `serviceType`: The type of service to advertise. This should be a short text string that describes the app’s networking protocol, in the same format as a Bonjour service type (without the transport protocol) and meeting the restrictions of https://tools.ietf.org/html/rfc6335 (section 5.1) governing Service Name Syntax. In particular, the string: Must be 1–15 characters long Can contain only ASCII lowercase letters, numbers, and hyphens Must contain at least one ASCII letter Must not begin or end with a hyphen Must not contain hyphens adjacent to other hyphens. This name should be easily distinguished from unrelated services. For example, a text chat app made by ABC company could use the service type abc-txtchat. For more details, read https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/NetServices/Articles/domainnames.html#//apple_ref/doc/uid/TP40002460.
- `info`: A dictionary of key-value pairs that are made available to browsers. Each key and value must be an NSString object. This data is advertised using a Bonjour TXT record, encoded according to http://tools.ietf.org/html/rfc6763 (section 6). As a result: The key-value pair must be no longer than 255 bytes (total) when encoded in UTF-8 format with an equals sign (=) between the key and the value. Keys cannot contain an equals sign. For optimal performance, the total size of the keys and values in this dictionary should be no more than about 400 bytes so that the entire advertisement can fit within a single Bluetooth data packet. For details on the maximum allowable length, read https://developer.apple.com/library/archive/documentation/Networking/Conceptual/NSNetServiceProgGuide/Articles/ResolvingServices.html#//apple_ref/doc/uid/20001078-SW3. If the data you need to provide is too large to fit within these constraints, create a custom discovery class using Bonjour for discovery and your choice of networking protocols for exchanging the information.
- `session`: The session into which new peers should be added after they accept the invitation.

## Return Value

Return Value An initialized instance, or nil if an error occurred.

## Discussion

Discussion This method throws an exception if a valid peerID object is not provided, or if serviceType is not a legal Bonjour service type.

## See Also

### Initializing and Configuring

- [session](multipeerconnectivity/mcadvertiserassistant/session.md)
- [delegate](multipeerconnectivity/mcadvertiserassistant/delegate.md)
- [discoveryInfo](multipeerconnectivity/mcadvertiserassistant/discoveryinfo.md)
- [serviceType](multipeerconnectivity/mcadvertiserassistant/servicetype.md)