diff --git a/src/Ember/Server/index.ts b/src/Ember/Server/index.ts
index b063f87..3e53f21 100644
--- a/src/Ember/Server/index.ts
+++ b/src/Ember/Server/index.ts
@@ -1,4 +1,392 @@
-const EmberServer = null
+import { EventEmitter } from 'events'
+import { S101Server } from '../Socket/S101Server'
+import { S101Client } from '../Socket'
+import {
+	EmberElement,
+	NumberedTreeNodeImpl,
+	ElementType,
+	EmberFunction,
+	InvocationResult,
+	EmberNode,
+	Parameter,
+	MatrixImpl,
+	Matrix,
+	Connections
+} from '../../model'
+import {
+	Collection,
+	RootElement,
+	NumberedTreeNode,
+	QualifiedElement,
+	RootType,
+	TreeElement,
+	EmberValue
+} from '../../types/types'
+import { DecodeResult } from '../../encodings/ber/decoder/DecodeResult'
+import { toQualifiedEmberNode } from '../Lib/util'
+import { berEncode } from '../../encodings/ber'
+import { Command, CommandType, FieldFlags, GetDirectory, Invoke } from '../../model/Command'
+import { Connection, ConnectionOperation, ConnectionImpl } from '../../model/Connection'
+import { InvocationResultImpl } from '../../model/InvocationResult'
+
 const ServerEvents = null
 
 export { EmberServer, ServerEvents }
+
+class EmberServer extends EventEmitter {
+	address: string | undefined
+	port: number
+	tree: Collection<NumberedTreeNode<EmberElement>> = {}
+
+	onInvocation?: (
+		emberFunction: NumberedTreeNode<EmberFunction>,
+		invocation: NumberedTreeNode<Invoke>
+	) => Promise<InvocationResult>
+	onSetValue?: (parameter: NumberedTreeNode<Parameter>, value: EmberValue) => Promise<boolean>
+	onMatrixOperation?: (Matrix: NumberedTreeNode<Matrix>, connection: Connections) => Promise<void>
+
+	private _server: S101Server
+	private _clients: Set<S101Client> = new Set()
+	private _subscriptions: { [path: string]: Array<S101Client> } = {}
+
+	constructor(port: number, address?: string) {
+		super()
+
+		this.address = address
+		this.port = port
+		this._server = new S101Server(port, address)
+
+		this._server.on('connection', (client: S101Client) => {
+			this._clients.add(client)
+
+			client.on('emberTree', (tree: DecodeResult<Collection<RootElement>>) =>
+				this._handleIncoming(tree, client)
+			)
+
+			client.on('disconnected', () => {
+				this._clearSubscription(client)
+				this._clients.delete(client)
+			})
+		})
+	}
+
+	init(tree: Collection<NumberedTreeNode<EmberElement>>) {
+		const setParent = (
+			parent: NumberedTreeNode<EmberElement>,
+			child: NumberedTreeNode<EmberElement>
+		) => {
+			child.parent = parent
+			if (child.children) {
+				for (const c of Object.values(child.children)) {
+					setParent(child, c)
+				}
+			}
+		}
+		for (const rootEl of Object.values(tree)) {
+			if (rootEl.children) {
+				for (const c of Object.values(rootEl.children)) {
+					setParent(rootEl, c)
+				}
+			}
+		}
+		this.tree = tree
+		this._server.listen()
+	}
+
+	discard() {
+		this._clients.forEach((c) => {
+			c.removeAllListeners()
+		})
+		this._clients.clear()
+		this._server.server?.close()
+	}
+
+	update<T extends EmberElement>(element: NumberedTreeNode<T>, update: Partial<T>) {
+		if (element.contents.type === ElementType.Matrix) {
+			const matrix: NumberedTreeNode<Matrix> = element as NumberedTreeNode<Matrix>
+			const matrixUpdate: Partial<Matrix> = update as Partial<Matrix>
+
+			if (matrixUpdate.connections) {
+				for (const connection of Object.values(matrixUpdate.connections!)) {
+					this.updateMatrixConnection(matrix, connection)
+				}
+			}
+		}
+		for (const [key, value] of Object.entries(update)) {
+			element.contents[key as keyof T] = value
+		}
+		const el = toQualifiedEmberNode(element)
+		const data = berEncode([el], RootType.Elements)
+		let elPath = el.path
+		if (el.contents.type !== ElementType.Node && !('targets' in update || 'sources' in update)) {
+			elPath = elPath.slice(0, -2) // remove the last element number
+		}
+
+		for (const [path, clients] of Object.entries(this._subscriptions)) {
+			if (elPath === path) {
+				clients.forEach((client) => {
+					client.sendBER(data)
+				})
+			}
+		}
+	}
+
+	updateMatrixConnection(element: NumberedTreeNode<Matrix>, update: Connection) {
+		if (!element.contents.connections) element.contents.connections = {}
+		let connection = element.contents.connections[update.target]
+		if (!connection) {
+			element.contents.connections[update.target] = new ConnectionImpl(update.target, [])
+			connection = element.contents.connections[update.target]
+		}
+		switch (update.operation) {
+			case ConnectionOperation.Connect:
+				for (const source of update.sources || []) {
+					if (!connection.sources!.find((v) => v === source)) {
+						connection.sources!.push(source)
+					}
+				}
+				break
+			case ConnectionOperation.Disconnect:
+				for (const source of update.sources || []) {
+					connection.sources?.forEach((oldSource, i) => {
+						if (source === oldSource) {
+							connection.sources!.splice(i, 1)
+						}
+					})
+				}
+				break
+			case ConnectionOperation.Absolute:
+			default:
+				connection.sources = update.sources
+				break
+		}
+
+		const qualified = toQualifiedEmberNode(element) as QualifiedElement<Matrix>
+		qualified.contents = new MatrixImpl(qualified.contents.identifier, undefined, undefined, {
+			[connection.target]: connection
+		})
+		const data = berEncode([qualified], RootType.Elements)
+
+		for (const [path, clients] of Object.entries(this._subscriptions)) {
+			if (qualified.path === path) {
+				clients.forEach((client) => {
+					client.sendBER(data)
+				})
+			}
+		}
+	}
+
+	private _handleIncoming(incoming: DecodeResult<Collection<RootElement>>, client: S101Client) {
+		for (const rootEl of Object.values(incoming.value)) {
+			if (rootEl.contents.type === ElementType.Command) {
+				// command on root
+				this._handleCommand('', rootEl as NumberedTreeNode<Command>, client)
+			} else {
+				this._handleNode((rootEl as QualifiedElement<EmberElement>).path || '', rootEl, client)
+			}
+		}
+	}
+
+	private _handleNode(
+		path: string,
+		el: QualifiedElement<EmberElement> | NumberedTreeNode<EmberElement>,
+		client: S101Client
+	) {
+		const children = Object.values(el.children || {})
+
+		if (children[0] && children[0].contents.type === ElementType.Command) {
+			this._handleCommand(path, children[0] as NumberedTreeNode<Command>, client)
+			return
+		} else if (el.contents.type === ElementType.Matrix && 'connections' in el.contents) {
+			this._handleMatrix(path, el as QualifiedElement<Matrix> | NumberedTreeNode<Matrix>)
+		}
+
+		if (!el.children) {
+			if (el.contents.type === ElementType.Parameter) {
+				this._handleSetValue(
+					path,
+					el as QualifiedElement<Parameter> | NumberedTreeNode<Parameter>,
+					client
+				)
+			}
+		} else {
+			for (const c of children) {
+				this._handleNode(path + c.number, c, client)
+			}
+		}
+	}
+
+	private _handleMatrix(path: string, el: QualifiedElement<Matrix> | NumberedTreeNode<Matrix>) {
+		if (this.onMatrixOperation) {
+			const tree = this.getElementByPath(path)
+			if (!tree || tree.contents.type !== ElementType.Matrix || !el.contents.connections) return
+
+			this.onMatrixOperation(tree as NumberedTreeNode<Matrix>, el.contents.connections)
+		}
+	}
+
+	private async _handleSetValue(
+		path: string,
+		el: QualifiedElement<Parameter> | NumberedTreeNode<Parameter>,
+		client: S101Client
+	) {
+		const tree = this.getElementByPath(path)
+		if (!tree || tree.contents.type !== ElementType.Parameter || el.contents.value === undefined)
+			return
+
+		let success = false
+		if (this.onSetValue) {
+			success = await this.onSetValue(tree as NumberedTreeNode<Parameter>, el.contents.value!)
+		}
+
+		if (!success) {
+			const qualified = toQualifiedEmberNode(tree)
+			const encoded = berEncode([qualified], RootType.Elements)
+
+			client.sendBER(encoded)
+		}
+	}
+
+	private async _handleCommand(path: string, el: NumberedTreeNode<Command>, client: S101Client) {
+		const tree = path ? this.getElementByPath(path) : this.tree
+		console.dir(tree, { depth: null })
+		if (!tree) return
+
+		if (el.contents.number === CommandType.Subscribe) {
+			this._subscribe(path, client)
+		} else if (el.contents.number === CommandType.Unsubscribe) {
+			this._unsubscribe(path, client)
+		} else if (el.contents.number === CommandType.GetDirectory) {
+			this._subscribe(path, client) // send updates to client
+			this._handleGetDirectory(
+				tree,
+				(el.contents as GetDirectory).dirFieldMask || FieldFlags.Default,
+				client
+			)
+		} else if (el.contents.number === CommandType.Invoke) {
+			let result: InvocationResult
+			if (this.onInvocation) {
+				result = await this.onInvocation(
+					tree as NumberedTreeNode<EmberFunction>,
+					el as NumberedTreeNode<Invoke>
+				)
+			} else {
+				result = new InvocationResultImpl(
+					(el as NumberedTreeNode<Invoke>).contents.invocation!.id || -1,
+					false
+				)
+			}
+			const encoded = berEncode(result, RootType.InvocationResult)
+			client.sendBER(encoded)
+		}
+	}
+
+	getElementByPath(path: string) {
+		const getNext = (elements: Collection<NumberedTreeNode<EmberElement>>, i?: string) =>
+			Object.values(elements || {}).find(
+				(r) =>
+					r.number === Number(i) ||
+					(r.contents as EmberNode).identifier === i ||
+					(r.contents as EmberNode).description === i
+			)
+		const getNextChild = (node: TreeElement<EmberElement>, i: string) =>
+			node.children && getNext(node.children, i)
+
+		const numberedPath: Array<number> = []
+		const pathArr = path.split('.')
+		const i = pathArr.shift()
+		let tree: NumberedTreeNode<EmberElement> | undefined = getNext(this.tree, i)
+		if (tree?.number) numberedPath.push(tree?.number)
+
+		while (pathArr.length) {
+			const i = pathArr.shift()
+			if (!i) break
+			if (!tree) break
+			const next = getNextChild(tree, i)
+			if (!next) {
+				// not found
+				return
+			}
+			tree = next
+			if (!tree) return
+			if (tree?.number) numberedPath.push(tree?.number)
+		}
+
+		return tree
+	}
+
+	private _subscribe(path: string, client: S101Client) {
+		this._subscriptions[path] = [...(this._subscriptions[path] || []), client]
+	}
+	private _unsubscribe(path: string, client: S101Client) {
+		if (!this._subscriptions[path]) return
+
+		this._subscriptions[path].forEach((c, i) => {
+			if (c === client) {
+				this._subscriptions[path].splice(i, 1)
+			}
+		})
+	}
+	private _clearSubscription(client: S101Client) {
+		for (const path of Object.keys(this._subscriptions)) {
+			this._unsubscribe(path, client)
+		}
+	}
+
+	private _handleGetDirectory(
+		tree: Collection<NumberedTreeNode<EmberElement>> | NumberedTreeNode<EmberElement>,
+		_dirFieldMasks: FieldFlags,
+		client: S101Client
+	) {
+		if (tree === this.tree) {
+			// getDir on root
+			const response: Collection<NumberedTreeNode<EmberElement>> = { ...this.tree }
+			for (const [i, rootEl] of Object.entries(this.tree)) {
+				response[(i as unknown) as number] = new NumberedTreeNodeImpl(
+					rootEl.number,
+					rootEl.contents
+				)
+			}
+			const data = berEncode(response, RootType.Elements)
+			client.sendBER(data)
+		} else {
+			const qualified = toQualifiedEmberNode(tree as NumberedTreeNode<EmberElement>)
+			qualified.children = {} // destroy ref to this.tree
+			if ('children' in tree && tree.children) {
+				for (const [i, child] of Object.entries(tree.children)) {
+					if (child.contents.type === ElementType.Matrix) {
+						// matrix should not have connections, targets and sources:
+						qualified.children[(i as unknown) as number] = new NumberedTreeNodeImpl(
+							child.number,
+							new MatrixImpl(
+								child.contents.identifier,
+								undefined,
+								undefined,
+								undefined,
+								child.contents.description,
+								child.contents.matrixType,
+								child.contents.addressingMode,
+								child.contents.targetCount,
+								child.contents.sourceCount,
+								child.contents.maximumTotalConnects,
+								child.contents.maximumConnectsPerTarget,
+								child.contents.parametersLocation,
+								child.contents.gainParameterNumber,
+								child.contents.labels,
+								child.contents.schemaIdentifiers,
+								child.contents.templateReference
+							)
+						)
+					} else {
+						qualified.children[(i as unknown) as number] = new NumberedTreeNodeImpl(
+							child.number,
+							child.contents
+						)
+					}
+				}
+			}
+			const data = berEncode([qualified as RootElement], RootType.Elements)
+			client.sendBER(data)
+		}
+	}
+}
diff --git a/src/Ember/Socket/S101Server.ts b/src/Ember/Socket/S101Server.ts
new file mode 100644
index 0000000..05b8a8e
--- /dev/null
+++ b/src/Ember/Socket/S101Server.ts
@@ -0,0 +1,51 @@
+import { EventEmitter } from 'events'
+import { Socket, createServer, Server } from 'net'
+import S101Socket from './S101Socket'
+
+export class S101Server extends EventEmitter {
+	port: number
+	address: string | undefined
+	server: Server | null
+	status: string // TODO - enum
+
+	constructor(port: number, address?: string) {
+		super()
+		this.port = port
+		this.address = address
+		this.server = null
+		this.status = 'disconnected'
+	}
+
+	addClient(socket: Socket) {
+		// Wrap the tcp socket into an S101Socket.
+		const client = new S101Socket(socket)
+		this.emit('connection', client)
+	}
+
+	listen() {
+		return new Promise((resolve, reject) => {
+			if (this.status !== 'disconnected') {
+				return reject(new Error('Already listening'))
+			}
+			this.server = createServer((socket) => {
+				this.addClient(socket)
+			})
+				.on('error', (e) => {
+					this.emit('error', e)
+					if (this.status === 'disconnected') {
+						return reject(e)
+					}
+				})
+				.on('listening', () => {
+					this.emit('listening')
+					this.status = 'listening'
+					resolve()
+				})
+			this.server.listen(this.port, this.address)
+		})
+	}
+
+	discard() {
+		this.server?.close()
+	}
+}