diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 226720f..18f9840 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -45,6 +45,7 @@ jobs:
 
       - name: Install dependencies
         run: |
+          sudo apt -y update && sudo apt -y install protobuf-compiler
           make common
 
       - name: lint
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f62f95e..e61ebec 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -50,6 +50,10 @@ jobs:
         path: ${{ steps.go-cache-paths.outputs.go-mod }}
         key: ${{ runner.os }}-${{ steps.go-cache-paths.outputs.go-version }}-mod-${{ hashFiles('**/go.mod', '**/go.sum') }}
 
+    - name: Install dependencies
+      run: |
+        sudo apt -y update && sudo apt -y install protobuf-compiler
+
     - name: Build applications
       run: |
         echo "Building with $(nproc) threads"
diff --git a/.gitignore b/.gitignore
index 7296465..9a623dc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@ vendor/
 
 *_easyjson.go
 *.pem
+*.pb.go
 *.prof
 *.socket
 *.tar.gz
diff --git a/Dockerfile b/Dockerfile
index 1418601..3887ba5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,6 +3,7 @@ FROM golang:1.18 AS builder
 WORKDIR /workdir
 
 COPY . .
+RUN apt -y update && apt -y install protobuf-compiler
 RUN make build
 
 FROM alpine:3.15
diff --git a/Makefile b/Makefile
index e1ca9ea..8cd998f 100644
--- a/Makefile
+++ b/Makefile
@@ -56,6 +56,14 @@ $(GOPATHBIN)/easyjson:
 	$(GO) get -u -d github.com/mailru/easyjson/...
 	$(GO) install github.com/mailru/easyjson/...
 
+$(GOPATHBIN)/protoc-gen-go:
+	$(GO) get -u -d google.golang.org/protobuf/cmd/protoc-gen-go
+	$(GO) install google.golang.org/protobuf/cmd/protoc-gen-go
+
+$(GOPATHBIN)/protoc-gen-go-grpc:
+	$(GO) get -u -d google.golang.org/grpc/cmd/protoc-gen-go-grpc
+	$(GO) install google.golang.org/grpc/cmd/protoc-gen-go-grpc
+
 continentmap.go:
 	$(CURDIR)/scripts/get_continent_map.py $@
 
@@ -70,7 +78,7 @@ check-continentmap:
 get:
 	$(GO) get $(PACKAGE)
 
-fmt: hook
+fmt: hook | common_proto
 	$(GOFMT) -s -w *.go client proxy server
 
 vet: common
@@ -83,23 +91,36 @@ cover: vet common
 	rm -f cover.out && \
 	$(GO) test -v -timeout $(TIMEOUT) -coverprofile cover.out $(ALL_PACKAGES) && \
 	sed -i "/_easyjson/d" cover.out && \
+	sed -i "/\.pb\.go/d" cover.out && \
 	$(GO) tool cover -func=cover.out
 
 coverhtml: vet common
 	rm -f cover.out && \
 	$(GO) test -v -timeout $(TIMEOUT) -coverprofile cover.out $(ALL_PACKAGES) && \
 	sed -i "/_easyjson/d" cover.out && \
+	sed -i "/\.pb\.go/d" cover.out && \
 	$(GO) tool cover -html=cover.out -o coverage.html
 
-%_easyjson.go: %.go $(GOPATHBIN)/easyjson
+%_easyjson.go: %.go $(GOPATHBIN)/easyjson | common_proto
 	PATH="$(GODIR)":$(PATH) "$(GOPATHBIN)/easyjson" -all $*.go
 
-common: \
+%.pb.go: %.proto $(GOPATHBIN)/protoc-gen-go $(GOPATHBIN)/protoc-gen-go-grpc
+	PATH="$(GODIR)":"$(GOPATHBIN)":$(PATH) protoc --go_out=. --go_opt=paths=source_relative \
+		--go-grpc_out=. --go-grpc_opt=paths=source_relative \
+		$*.proto
+
+common: common_easyjson common_proto
+
+common_easyjson: \
 	api_async_easyjson.go \
 	api_backend_easyjson.go \
 	api_proxy_easyjson.go \
 	api_signaling_easyjson.go
 
+common_proto: \
+	grpc_mcu.pb.go \
+	grpc_sessions.pb.go
+
 $(BINDIR):
 	mkdir -p $(BINDIR)
 
@@ -115,6 +136,7 @@ proxy: common $(BINDIR)
 clean:
 	rm -f *_easyjson.go
 	rm -f easyjson-bootstrap*.go
+	rm -f *.pb.go
 
 build: server proxy
 
diff --git a/README.md b/README.md
index 2b1afac..f9daabe 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ The following tools are required for building the signaling server.
 - git
 - go >= 1.17
 - make
+- protobuf-compiler >= 3
 
 All other dependencies are fetched automatically while building.
 
diff --git a/backend_server.go b/backend_server.go
index 81120d2..9998c33 100644
--- a/backend_server.go
+++ b/backend_server.go
@@ -22,6 +22,7 @@
 package signaling
 
 import (
+	"context"
 	"crypto/hmac"
 	"crypto/rand"
 	"crypto/sha1"
@@ -324,6 +325,8 @@ func (b *BackendServer) sendRoomDisinvite(roomid string, backend *Backend, reaso
 	}
 
 	timeout := time.Second
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
 	var wg sync.WaitGroup
 	for _, sessionid := range sessionids {
 		if sessionid == sessionIdNotInMeeting {
@@ -334,7 +337,7 @@ func (b *BackendServer) sendRoomDisinvite(roomid string, backend *Backend, reaso
 		wg.Add(1)
 		go func(sessionid string) {
 			defer wg.Done()
-			if sid, err := b.lookupByRoomSessionId(sessionid, nil, timeout); err != nil {
+			if sid, err := b.lookupByRoomSessionId(ctx, sessionid, nil); err != nil {
 				log.Printf("Could not lookup by room session %s: %s", sessionid, err)
 			} else if sid != "" {
 				if err := b.events.PublishSessionMessage(sid, backend, msg); err != nil {
@@ -377,7 +380,7 @@ func (b *BackendServer) sendRoomUpdate(roomid string, backend *Backend, notified
 	}
 }
 
-func (b *BackendServer) lookupByRoomSessionId(roomSessionId string, cache *ConcurrentStringStringMap, timeout time.Duration) (string, error) {
+func (b *BackendServer) lookupByRoomSessionId(ctx context.Context, roomSessionId string, cache *ConcurrentStringStringMap) (string, error) {
 	if roomSessionId == sessionIdNotInMeeting {
 		log.Printf("Trying to lookup empty room session id: %s", roomSessionId)
 		return "", nil
@@ -389,7 +392,7 @@ func (b *BackendServer) lookupByRoomSessionId(roomSessionId string, cache *Concu
 		}
 	}
 
-	sid, err := b.roomSessions.GetSessionId(roomSessionId)
+	sid, err := b.roomSessions.LookupSessionId(ctx, roomSessionId)
 	if err == ErrNoSuchRoomSession {
 		return "", nil
 	} else if err != nil {
@@ -402,7 +405,7 @@ func (b *BackendServer) lookupByRoomSessionId(roomSessionId string, cache *Concu
 	return sid, nil
 }
 
-func (b *BackendServer) fixupUserSessions(cache *ConcurrentStringStringMap, users []map[string]interface{}, timeout time.Duration) []map[string]interface{} {
+func (b *BackendServer) fixupUserSessions(ctx context.Context, cache *ConcurrentStringStringMap, users []map[string]interface{}) []map[string]interface{} {
 	if len(users) == 0 {
 		return users
 	}
@@ -430,7 +433,7 @@ func (b *BackendServer) fixupUserSessions(cache *ConcurrentStringStringMap, user
 		wg.Add(1)
 		go func(roomSessionId string, u map[string]interface{}) {
 			defer wg.Done()
-			if sessionId, err := b.lookupByRoomSessionId(roomSessionId, cache, timeout); err != nil {
+			if sessionId, err := b.lookupByRoomSessionId(ctx, roomSessionId, cache); err != nil {
 				log.Printf("Could not lookup by room session %s: %s", roomSessionId, err)
 				delete(u, "sessionId")
 			} else if sessionId != "" {
@@ -456,11 +459,13 @@ func (b *BackendServer) sendRoomIncall(roomid string, backend *Backend, request
 	if !request.InCall.All {
 		timeout := time.Second
 
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
 		var cache ConcurrentStringStringMap
 		// Convert (Nextcloud) session ids to signaling session ids.
-		request.InCall.Users = b.fixupUserSessions(&cache, request.InCall.Users, timeout)
+		request.InCall.Users = b.fixupUserSessions(ctx, &cache, request.InCall.Users)
 		// Entries in "Changed" are most likely already fetched through the "Users" list.
-		request.InCall.Changed = b.fixupUserSessions(&cache, request.InCall.Changed, timeout)
+		request.InCall.Changed = b.fixupUserSessions(ctx, &cache, request.InCall.Changed)
 
 		if len(request.InCall.Users) == 0 && len(request.InCall.Changed) == 0 {
 			return nil
@@ -478,9 +483,11 @@ func (b *BackendServer) sendRoomParticipantsUpdate(roomid string, backend *Backe
 	timeout := time.Second
 
 	// Convert (Nextcloud) session ids to signaling session ids.
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
 	var cache ConcurrentStringStringMap
-	request.Participants.Users = b.fixupUserSessions(&cache, request.Participants.Users, timeout)
-	request.Participants.Changed = b.fixupUserSessions(&cache, request.Participants.Changed, timeout)
+	request.Participants.Users = b.fixupUserSessions(ctx, &cache, request.Participants.Users)
+	request.Participants.Changed = b.fixupUserSessions(ctx, &cache, request.Participants.Changed)
 
 	if len(request.Participants.Users) == 0 && len(request.Participants.Changed) == 0 {
 		return nil
diff --git a/backend_server_test.go b/backend_server_test.go
index e14b740..bc0acfa 100644
--- a/backend_server_test.go
+++ b/backend_server_test.go
@@ -88,7 +88,7 @@ func CreateBackendServerForTestFromConfig(t *testing.T, config *goconf.ConfigFil
 	config.AddOption("clients", "internalsecret", string(testInternalSecret))
 	config.AddOption("geoip", "url", "none")
 	events := getAsyncEventsForTest(t)
-	hub, err := NewHub(config, events, r, "no-version")
+	hub, err := NewHub(config, events, nil, r, "no-version")
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/clientsession.go b/clientsession.go
index 3d447ef..c958937 100644
--- a/clientsession.go
+++ b/clientsession.go
@@ -75,6 +75,9 @@ type ClientSession struct {
 	room          unsafe.Pointer
 	roomSessionId string
 
+	publisherWaitersId uint64
+	publisherWaiters   map[uint64]chan bool
+
 	publishers  map[string]McuPublisher
 	subscribers map[string]McuSubscriber
 
@@ -803,6 +806,26 @@ func (s *ClientSession) checkOfferTypeLocked(streamType string, data *MessageCli
 	return 0, nil
 }
 
+func (s *ClientSession) wakeupPublisherWaiters() {
+	for _, ch := range s.publisherWaiters {
+		ch <- true
+	}
+}
+
+func (s *ClientSession) addPublisherWaiter(ch chan bool) uint64 {
+	if s.publisherWaiters == nil {
+		s.publisherWaiters = make(map[uint64]chan bool)
+	}
+	id := s.publisherWaitersId + 1
+	s.publisherWaitersId = id
+	s.publisherWaiters[id] = ch
+	return id
+}
+
+func (s *ClientSession) removePublisherWaiter(id uint64) {
+	delete(s.publisherWaiters, id)
+}
+
 func (s *ClientSession) GetOrCreatePublisher(ctx context.Context, mcu Mcu, streamType string, data *MessageClientMessageData) (McuPublisher, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -851,6 +874,7 @@ func (s *ClientSession) GetOrCreatePublisher(ctx context.Context, mcu Mcu, strea
 			s.publishers[streamType] = publisher
 		}
 		log.Printf("Publishing %s as %s for session %s", streamType, publisher.Id(), s.PublicId())
+		s.wakeupPublisherWaiters()
 	} else {
 		publisher.SetMedia(mediaTypes)
 	}
@@ -858,11 +882,44 @@ func (s *ClientSession) GetOrCreatePublisher(ctx context.Context, mcu Mcu, strea
 	return publisher, nil
 }
 
+func (s *ClientSession) getPublisherLocked(streamType string) McuPublisher {
+	return s.publishers[streamType]
+}
+
 func (s *ClientSession) GetPublisher(streamType string) McuPublisher {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	return s.publishers[streamType]
+	return s.getPublisherLocked(streamType)
+}
+
+func (s *ClientSession) GetOrWaitForPublisher(ctx context.Context, streamType string) McuPublisher {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	publisher := s.getPublisherLocked(streamType)
+	if publisher != nil {
+		return publisher
+	}
+
+	ch := make(chan bool, 1)
+	id := s.addPublisherWaiter(ch)
+	defer s.removePublisherWaiter(id)
+
+	for {
+		s.mu.Unlock()
+		select {
+		case <-ch:
+			s.mu.Lock()
+			publisher := s.getPublisherLocked(streamType)
+			if publisher != nil {
+				return publisher
+			}
+		case <-ctx.Done():
+			s.mu.Lock()
+			return nil
+		}
+	}
 }
 
 func (s *ClientSession) GetOrCreateSubscriber(ctx context.Context, mcu Mcu, id string, streamType string) (McuSubscriber, error) {
diff --git a/grpc_client.go b/grpc_client.go
new file mode 100644
index 0000000..ce32b89
--- /dev/null
+++ b/grpc_client.go
@@ -0,0 +1,225 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2022 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package signaling
+
+import (
+	"context"
+	"log"
+	"net"
+	"strings"
+	"sync"
+
+	"github.com/dlintw/goconf"
+	"google.golang.org/grpc"
+	codes "google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/insecure"
+	status "google.golang.org/grpc/status"
+)
+
+type grpcClientImpl struct {
+	RpcMcuClient
+	RpcSessionsClient
+}
+
+func newGrpcClientImpl(conn grpc.ClientConnInterface) *grpcClientImpl {
+	return &grpcClientImpl{
+		RpcMcuClient:      NewRpcMcuClient(conn),
+		RpcSessionsClient: NewRpcSessionsClient(conn),
+	}
+}
+
+type GrpcClient struct {
+	conn *grpc.ClientConn
+	impl *grpcClientImpl
+}
+
+func NewGrpcClient(target string) (*GrpcClient, error) {
+	conn, err := grpc.Dial(target, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		return nil, err
+	}
+
+	result := &GrpcClient{
+		conn: conn,
+		impl: newGrpcClientImpl(conn),
+	}
+	return result, nil
+}
+
+func (c *GrpcClient) Target() string {
+	return c.conn.Target()
+}
+
+func (c *GrpcClient) Close() error {
+	return c.conn.Close()
+}
+
+func (c *GrpcClient) LookupSessionId(ctx context.Context, roomSessionId string) (string, error) {
+	// TODO: Remove debug logging
+	log.Printf("Lookup room session %s on %s", roomSessionId, c.Target())
+	response, err := c.impl.LookupSessionId(ctx, &LookupSessionIdRequest{
+		RoomSessionId: roomSessionId,
+	}, grpc.WaitForReady(true))
+	if s, ok := status.FromError(err); ok && s.Code() == codes.NotFound {
+		return "", ErrNoSuchRoomSession
+	} else if err != nil {
+		return "", err
+	}
+
+	sessionId := response.GetSessionId()
+	if sessionId == "" {
+		return "", ErrNoSuchRoomSession
+	}
+
+	return sessionId, nil
+}
+
+func (c *GrpcClient) IsSessionInCall(ctx context.Context, sessionId string, room *Room) (bool, error) {
+	// TODO: Remove debug logging
+	log.Printf("Check if session %s is in call %s on %s", sessionId, room.Id(), c.Target())
+	response, err := c.impl.IsSessionInCall(ctx, &IsSessionInCallRequest{
+		SessionId:  sessionId,
+		RoomId:     room.Id(),
+		BackendUrl: room.Backend().url,
+	}, grpc.WaitForReady(true))
+	if s, ok := status.FromError(err); ok && s.Code() == codes.NotFound {
+		return false, nil
+	} else if err != nil {
+		return false, err
+	}
+
+	return response.GetInCall(), nil
+}
+
+func (c *GrpcClient) GetPublisherId(ctx context.Context, sessionId string, streamType string) (string, string, net.IP, error) {
+	// TODO: Remove debug logging
+	log.Printf("Get %s publisher id %s on %s", streamType, sessionId, c.Target())
+	response, err := c.impl.GetPublisherId(ctx, &GetPublisherIdRequest{
+		SessionId:  sessionId,
+		StreamType: streamType,
+	}, grpc.WaitForReady(true))
+	if s, ok := status.FromError(err); ok && s.Code() == codes.NotFound {
+		return "", "", nil, nil
+	} else if err != nil {
+		return "", "", nil, err
+	}
+
+	return response.GetPublisherId(), response.GetProxyUrl(), net.ParseIP(response.GetIp()), nil
+}
+
+type GrpcClients struct {
+	mu sync.RWMutex
+
+	clientsMap map[string]*GrpcClient
+	clients    []*GrpcClient
+}
+
+func NewGrpcClients(config *goconf.ConfigFile) (*GrpcClients, error) {
+	result := &GrpcClients{}
+	if err := result.load(config); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func (c *GrpcClients) load(config *goconf.ConfigFile) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	targets, _ := config.GetString("grpc", "targets")
+
+	clientsMap := make(map[string]*GrpcClient)
+	var clients []*GrpcClient
+	removeTargets := make(map[string]bool, len(c.clientsMap))
+	for target, client := range c.clientsMap {
+		removeTargets[target] = true
+		clientsMap[target] = client
+	}
+
+	for _, target := range strings.Split(targets, ",") {
+		target = strings.TrimSpace(target)
+		if target == "" {
+			continue
+		}
+
+		if client, found := clientsMap[target]; found {
+			clients = append(clients, client)
+			delete(removeTargets, target)
+			continue
+		}
+
+		client, err := NewGrpcClient(target)
+		if err != nil {
+			for target, client := range clientsMap {
+				if closeerr := client.Close(); closeerr != nil {
+					log.Printf("Error closing client to %s: %s", target, closeerr)
+				}
+			}
+			return err
+		}
+
+		log.Printf("Adding %s as GRPC target", target)
+		clientsMap[target] = client
+		clients = append(clients, client)
+	}
+
+	for target := range removeTargets {
+		if client, found := clientsMap[target]; found {
+			log.Printf("Deleting GRPC target %s", target)
+			if err := client.Close(); err != nil {
+				log.Printf("Error closing client to %s: %s", target, err)
+			}
+			delete(clientsMap, target)
+		}
+	}
+
+	c.clients = clients
+	c.clientsMap = clientsMap
+	return nil
+}
+
+func (c *GrpcClients) Reload(config *goconf.ConfigFile) {
+	if err := c.load(config); err != nil {
+		log.Printf("Could not reload RPC clients: %s", err)
+	}
+}
+
+func (c *GrpcClients) Close() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	for target, client := range c.clientsMap {
+		if err := client.Close(); err != nil {
+			log.Printf("Error closing client to %s: %s", target, err)
+		}
+	}
+
+	c.clients = nil
+	c.clientsMap = nil
+}
+
+func (c *GrpcClients) GetClients() []*GrpcClient {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	return c.clients
+}
diff --git a/grpc_mcu.proto b/grpc_mcu.proto
new file mode 100644
index 0000000..b2313d2
--- /dev/null
+++ b/grpc_mcu.proto
@@ -0,0 +1,41 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2022 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+syntax = "proto3";
+
+option go_package = "github.com/strukturag/nextcloud-spreed-signaling;signaling";
+
+package signaling;
+
+service RpcMcu {
+  rpc GetPublisherId(GetPublisherIdRequest) returns (GetPublisherIdReply) {}
+}
+
+message GetPublisherIdRequest {
+  string sessionId = 1;
+  string streamType = 2;
+}
+
+message GetPublisherIdReply {
+  string publisherId = 1;
+  string proxyUrl = 2;
+  string ip = 3;
+}
diff --git a/grpc_server.go b/grpc_server.go
new file mode 100644
index 0000000..7d4102f
--- /dev/null
+++ b/grpc_server.go
@@ -0,0 +1,141 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2022 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package signaling
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"net"
+
+	"github.com/dlintw/goconf"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	status "google.golang.org/grpc/status"
+)
+
+type GrpcServer struct {
+	UnimplementedRpcMcuServer
+	UnimplementedRpcSessionsServer
+
+	conn     *grpc.Server
+	listener net.Listener
+
+	hub *Hub
+}
+
+func NewGrpcServer(config *goconf.ConfigFile) (*GrpcServer, error) {
+	var listener net.Listener
+	if addr, _ := config.GetString("grpc", "listen"); addr != "" {
+		var err error
+		listener, err = net.Listen("tcp", addr)
+		if err != nil {
+			return nil, fmt.Errorf("could not create GRPC server: %w", err)
+		}
+	}
+
+	conn := grpc.NewServer()
+
+	result := &GrpcServer{
+		conn:     conn,
+		listener: listener,
+	}
+	RegisterRpcSessionsServer(conn, result)
+	RegisterRpcMcuServer(conn, result)
+	return result, nil
+}
+
+func (s *GrpcServer) Run() error {
+	if s.listener == nil {
+		return nil
+	}
+
+	return s.conn.Serve(s.listener)
+}
+
+func (s *GrpcServer) Close() {
+	s.conn.GracefulStop()
+}
+
+func (s *GrpcServer) LookupSessionId(ctx context.Context, request *LookupSessionIdRequest) (*LookupSessionIdReply, error) {
+	// TODO: Remove debug logging
+	log.Printf("Lookup session id for room session id %s", request.RoomSessionId)
+	sid, err := s.hub.roomSessions.GetSessionId(request.RoomSessionId)
+	if errors.Is(err, ErrNoSuchRoomSession) {
+		return nil, status.Error(codes.NotFound, "no such room session id")
+	} else if err != nil {
+		return nil, err
+	}
+
+	return &LookupSessionIdReply{
+		SessionId: sid,
+	}, nil
+}
+
+func (s *GrpcServer) IsSessionInCall(ctx context.Context, request *IsSessionInCallRequest) (*IsSessionInCallReply, error) {
+	// TODO: Remove debug logging
+	log.Printf("Check if session %s is in call %s on %s", request.SessionId, request.RoomId, request.BackendUrl)
+	session := s.hub.GetSessionByPublicId(request.SessionId)
+	if session == nil {
+		return nil, status.Error(codes.NotFound, "no such session id")
+	}
+
+	result := &IsSessionInCallReply{}
+	room := session.GetRoom()
+	if room == nil || room.Id() != request.GetRoomId() || room.Backend().url != request.GetBackendUrl() ||
+		(session.ClientType() != HelloClientTypeInternal && !room.IsSessionInCall(session)) {
+		// Recipient is not in a room, a different room or not in the call.
+		result.InCall = false
+	} else {
+		result.InCall = true
+	}
+	return result, nil
+}
+
+func (s *GrpcServer) GetPublisherId(ctx context.Context, request *GetPublisherIdRequest) (*GetPublisherIdReply, error) {
+	// TODO: Remove debug logging
+	log.Printf("Get %s publisher id for session %s", request.StreamType, request.SessionId)
+	session := s.hub.GetSessionByPublicId(request.SessionId)
+	if session == nil {
+		return nil, status.Error(codes.NotFound, "no such session")
+	}
+
+	clientSession, ok := session.(*ClientSession)
+	if !ok {
+		return nil, status.Error(codes.NotFound, "no such session")
+	}
+
+	publisher := clientSession.GetOrWaitForPublisher(ctx, request.StreamType)
+	if publisher, ok := publisher.(*mcuProxyPublisher); ok {
+		reply := &GetPublisherIdReply{
+			PublisherId: publisher.Id(),
+			ProxyUrl:    publisher.conn.rawUrl,
+		}
+		if ip := publisher.conn.ip; ip != nil {
+			reply.Ip = ip.String()
+		}
+		return reply, nil
+	}
+
+	return nil, status.Error(codes.NotFound, "no such publisher")
+}
diff --git a/grpc_sessions.proto b/grpc_sessions.proto
new file mode 100644
index 0000000..497a74f
--- /dev/null
+++ b/grpc_sessions.proto
@@ -0,0 +1,49 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2022 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+syntax = "proto3";
+
+option go_package = "github.com/strukturag/nextcloud-spreed-signaling;signaling";
+
+package signaling;
+
+service RpcSessions {
+  rpc LookupSessionId(LookupSessionIdRequest) returns (LookupSessionIdReply) {}
+  rpc IsSessionInCall(IsSessionInCallRequest) returns (IsSessionInCallReply) {}
+}
+
+message LookupSessionIdRequest {
+  string roomSessionId = 1;
+}
+
+message LookupSessionIdReply {
+  string sessionId = 1;
+}
+
+message IsSessionInCallRequest {
+  string sessionId = 1;
+  string roomId = 2;
+  string backendUrl = 3;
+}
+
+message IsSessionInCallReply {
+  bool inCall = 1;
+}
diff --git a/hub.go b/hub.go
index 403e38e..97b2a03 100644
--- a/hub.go
+++ b/hub.go
@@ -28,6 +28,7 @@ import (
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"hash/fnv"
 	"log"
@@ -148,9 +149,12 @@ type Hub struct {
 	geoip          *GeoLookup
 	geoipOverrides map[*net.IPNet]string
 	geoipUpdating  int32
+
+	rpcServer  *GrpcServer
+	rpcClients *GrpcClients
 }
 
-func NewHub(config *goconf.ConfigFile, events AsyncEvents, r *mux.Router, version string) (*Hub, error) {
+func NewHub(config *goconf.ConfigFile, events AsyncEvents, rpcClients *GrpcClients, r *mux.Router, version string) (*Hub, error) {
 	hashKey, _ := config.GetString("sessions", "hashkey")
 	switch len(hashKey) {
 	case 32:
@@ -210,7 +214,12 @@ func NewHub(config *goconf.ConfigFile, events AsyncEvents, r *mux.Router, versio
 		decodeCaches = append(decodeCaches, NewLruCache(decodeCacheSize))
 	}
 
-	roomSessions, err := NewBuiltinRoomSessions()
+	rpcServer, err := NewGrpcServer(config)
+	if err != nil {
+		return nil, err
+	}
+
+	roomSessions, err := NewBuiltinRoomSessions(rpcClients)
 	if err != nil {
 		return nil, err
 	}
@@ -338,8 +347,12 @@ func NewHub(config *goconf.ConfigFile, events AsyncEvents, r *mux.Router, versio
 
 		geoip:          geoip,
 		geoipOverrides: geoipOverrides,
+
+		rpcServer:  rpcServer,
+		rpcClients: rpcClients,
 	}
 	backend.hub = hub
+	rpcServer.hub = hub
 	hub.upgrader.CheckOrigin = hub.checkOrigin
 	r.HandleFunc("/spreed", func(w http.ResponseWriter, r *http.Request) {
 		hub.serveWs(w, r)
@@ -437,6 +450,12 @@ func (h *Hub) Run() {
 	go h.updateGeoDatabase()
 	h.roomPing.Start()
 	defer h.roomPing.Stop()
+	go func() {
+		if err := h.rpcServer.Run(); err != nil {
+			log.Fatalf("Could not start RPC server: %s", err)
+		}
+	}()
+	defer h.rpcServer.Close()
 
 	housekeeping := time.NewTicker(housekeepingInterval)
 	geoipUpdater := time.NewTicker(24 * time.Hour)
@@ -480,6 +499,7 @@ func (h *Hub) Reload(config *goconf.ConfigFile) {
 		h.mcu.Reload(config)
 	}
 	h.backend.Reload(config)
+	h.rpcClients.Reload(config)
 }
 
 func reverseSessionId(s string) (string, error) {
@@ -575,6 +595,10 @@ func (h *Hub) GetSessionByPublicId(sessionId string) Session {
 	h.mu.Lock()
 	session := h.sessions[data.Sid]
 	h.mu.Unlock()
+	if session != nil && session.PublicId() != sessionId {
+		// Session was created on different server.
+		return nil
+	}
 	return session
 }
 
@@ -1726,7 +1750,41 @@ func sendMcuProcessingFailed(session *ClientSession, message *ClientMessage) {
 	session.SendMessage(response)
 }
 
-func (h *Hub) isInSameCall(senderSession *ClientSession, recipientSessionId string) bool {
+func (h *Hub) isInSameCallRemote(ctx context.Context, senderSession *ClientSession, senderRoom *Room, recipientSessionId string) bool {
+	clients := h.rpcClients.GetClients()
+	if len(clients) == 0 {
+		return false
+	}
+
+	var result int32
+	var wg sync.WaitGroup
+	rpcCtx, cancel := context.WithCancel(ctx)
+	defer cancel()
+	for _, client := range clients {
+		wg.Add(1)
+		go func(client *GrpcClient) {
+			defer wg.Done()
+
+			inCall, err := client.IsSessionInCall(rpcCtx, recipientSessionId, senderRoom)
+			if errors.Is(err, context.Canceled) {
+				return
+			} else if err != nil {
+				log.Printf("Error checking session %s in call on %s: %s", recipientSessionId, client.Target(), err)
+				return
+			} else if !inCall {
+				return
+			}
+
+			cancel()
+			atomic.StoreInt32(&result, 1)
+		}(client)
+	}
+	wg.Wait()
+
+	return atomic.LoadInt32(&result) != 0
+}
+
+func (h *Hub) isInSameCall(ctx context.Context, senderSession *ClientSession, recipientSessionId string) bool {
 	if senderSession.ClientType() == HelloClientTypeInternal {
 		// Internal clients may subscribe all streams.
 		return true
@@ -1741,7 +1799,7 @@ func (h *Hub) isInSameCall(senderSession *ClientSession, recipientSessionId stri
 	recipientSession := h.GetSessionByPublicId(recipientSessionId)
 	if recipientSession == nil {
 		// Recipient session does not exist.
-		return false
+		return h.isInSameCallRemote(ctx, senderSession, senderRoom, recipientSessionId)
 	}
 
 	recipientRoom := recipientSession.GetRoom()
@@ -1770,7 +1828,7 @@ func (h *Hub) processMcuMessage(senderSession *ClientSession, session *ClientSes
 
 		// A user is only allowed to subscribe a stream if she is in the same room
 		// as the other user and both have their "inCall" flag set.
-		if !h.allowSubscribeAnyStream && !h.isInSameCall(senderSession, message.Recipient.SessionId) {
+		if !h.allowSubscribeAnyStream && !h.isInSameCall(ctx, senderSession, message.Recipient.SessionId) {
 			log.Printf("Session %s is not in the same call as session %s, not requesting offer", session.PublicId(), message.Recipient.SessionId)
 			sendNotAllowed(senderSession, client_message, "Not allowed to request offer.")
 			return
diff --git a/hub_test.go b/hub_test.go
index 39f9a50..8dc8b95 100644
--- a/hub_test.go
+++ b/hub_test.go
@@ -111,7 +111,7 @@ func CreateHubForTestWithConfig(t *testing.T, getConfigFunc func(*httptest.Serve
 	if err != nil {
 		t.Fatal(err)
 	}
-	h, err := NewHub(config, events, r, "no-version")
+	h, err := NewHub(config, events, nil, r, "no-version")
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/mcu_proxy.go b/mcu_proxy.go
index d395c82..1252351 100644
--- a/mcu_proxy.go
+++ b/mcu_proxy.go
@@ -26,6 +26,7 @@ import (
 	"crypto/rsa"
 	"crypto/tls"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -1006,20 +1007,13 @@ func (c *mcuProxyConnection) newPublisher(ctx context.Context, listener McuListe
 	return publisher, nil
 }
 
-func (c *mcuProxyConnection) newSubscriber(ctx context.Context, listener McuListener, publisher string, streamType string) (McuSubscriber, error) {
-	c.publishersLock.Lock()
-	id, found := c.publisherIds[publisher+"|"+streamType]
-	c.publishersLock.Unlock()
-	if !found {
-		return nil, fmt.Errorf("Unknown publisher %s", publisher)
-	}
-
+func (c *mcuProxyConnection) newSubscriber(ctx context.Context, listener McuListener, publisherId string, publisherSessionId string, streamType string) (McuSubscriber, error) {
 	msg := &ProxyClientMessage{
 		Type: "command",
 		Command: &CommandProxyClientMessage{
 			Type:        "create-subscriber",
 			StreamType:  streamType,
-			PublisherId: id,
+			PublisherId: publisherId,
 		},
 	}
 
@@ -1030,8 +1024,8 @@ func (c *mcuProxyConnection) newSubscriber(ctx context.Context, listener McuList
 	}
 
 	proxyId := response.Command.Id
-	log.Printf("Created %s subscriber %s on %s for %s", streamType, proxyId, c, publisher)
-	subscriber := newMcuProxySubscriber(publisher, response.Command.Sid, streamType, proxyId, c, listener)
+	log.Printf("Created %s subscriber %s on %s for %s", streamType, proxyId, c, publisherSessionId)
+	subscriber := newMcuProxySubscriber(publisherSessionId, response.Command.Sid, streamType, proxyId, c, listener)
 	c.subscribersLock.Lock()
 	c.subscribers[proxyId] = subscriber
 	c.subscribersLock.Unlock()
@@ -1075,9 +1069,11 @@ type mcuProxy struct {
 	publisherWaiters   map[uint64]chan bool
 
 	continentsMap atomic.Value
+
+	rpcClients *GrpcClients
 }
 
-func NewMcuProxy(config *goconf.ConfigFile, etcdClient *EtcdClient) (Mcu, error) {
+func NewMcuProxy(config *goconf.ConfigFile, etcdClient *EtcdClient, rpcClients *GrpcClients) (Mcu, error) {
 	urlType, _ := config.GetString("mcu", "urltype")
 	if urlType == "" {
 		urlType = proxyUrlTypeStatic
@@ -1139,6 +1135,8 @@ func NewMcuProxy(config *goconf.ConfigFile, etcdClient *EtcdClient) (Mcu, error)
 		publishers: make(map[string]*mcuProxyConnection),
 
 		publisherWaiters: make(map[uint64]chan bool),
+
+		rpcClients: rpcClients,
 	}
 
 	if err := mcu.loadContinentsMap(config); err != nil {
@@ -1850,19 +1848,18 @@ func (m *mcuProxy) NewPublisher(ctx context.Context, listener McuListener, id st
 	return nil, fmt.Errorf("No MCU connection available")
 }
 
-func (m *mcuProxy) getPublisherConnection(ctx context.Context, publisher string, streamType string) *mcuProxyConnection {
+func (m *mcuProxy) getPublisherConnection(publisher string, streamType string) *mcuProxyConnection {
 	m.mu.RLock()
-	conn := m.publishers[publisher+"|"+streamType]
-	m.mu.RUnlock()
-	if conn != nil {
-		return conn
-	}
+	defer m.mu.RUnlock()
 
-	log.Printf("No %s publisher %s found yet, deferring", streamType, publisher)
+	return m.publishers[publisher+"|"+streamType]
+}
+
+func (m *mcuProxy) waitForPublisherConnection(ctx context.Context, publisher string, streamType string) *mcuProxyConnection {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
-	conn = m.publishers[publisher+"|"+streamType]
+	conn := m.publishers[publisher+"|"+streamType]
 	if conn != nil {
 		// Publisher was created while waiting for lock.
 		return conn
@@ -1890,10 +1887,92 @@ func (m *mcuProxy) getPublisherConnection(ctx context.Context, publisher string,
 }
 
 func (m *mcuProxy) NewSubscriber(ctx context.Context, listener McuListener, publisher string, streamType string) (McuSubscriber, error) {
-	conn := m.getPublisherConnection(ctx, publisher, streamType)
-	if conn == nil {
-		return nil, fmt.Errorf("No %s publisher %s found", streamType, publisher)
+	if conn := m.getPublisherConnection(publisher, streamType); conn != nil {
+		// Fast common path: publisher is available locally.
+		conn.publishersLock.Lock()
+		id, found := conn.publisherIds[publisher+"|"+streamType]
+		conn.publishersLock.Unlock()
+		if !found {
+			return nil, fmt.Errorf("Unknown publisher %s", publisher)
+		}
+
+		return conn.newSubscriber(ctx, listener, id, publisher, streamType)
 	}
 
-	return conn.newSubscriber(ctx, listener, publisher, streamType)
+	log.Printf("No %s publisher %s found yet, deferring", streamType, publisher)
+	ch := make(chan McuSubscriber)
+	getctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	// Wait for publisher to be created locally.
+	go func() {
+		if conn := m.waitForPublisherConnection(getctx, publisher, streamType); conn != nil {
+			cancel() // Cancel pending RPC calls.
+
+			conn.publishersLock.Lock()
+			id, found := conn.publisherIds[publisher+"|"+streamType]
+			conn.publishersLock.Unlock()
+			if !found {
+				log.Printf("Unknown id for local %s publisher %s", streamType, publisher)
+				return
+			}
+
+			subscriber, err := conn.newSubscriber(ctx, listener, id, publisher, streamType)
+			if subscriber != nil {
+				ch <- subscriber
+			} else if err != nil {
+				log.Printf("Error creating local subscriber for %s publisher %s: %s", streamType, publisher, err)
+			}
+		}
+	}()
+
+	// Wait for publisher to be created on one of the other servers in the cluster.
+	if clients := m.rpcClients.GetClients(); len(clients) > 0 {
+		for _, client := range clients {
+			go func(client *GrpcClient) {
+				id, url, ip, err := client.GetPublisherId(getctx, publisher, streamType)
+				if errors.Is(err, context.Canceled) {
+					return
+				} else if err != nil {
+					log.Printf("Error getting %s publisher id %s from %s: %s", streamType, publisher, client.Target(), err)
+					return
+				} else if id == "" {
+					// Publisher not found on other server
+					return
+				}
+
+				cancel() // Cancel pending RPC calls.
+				log.Printf("Found publisher id %s through %s on proxy %s", id, client.Target(), url)
+
+				m.connectionsMu.RLock()
+				connections := m.connections
+				m.connectionsMu.RUnlock()
+				for _, conn := range connections {
+					if conn.rawUrl != url || !ip.Equal(conn.ip) {
+						continue
+					}
+
+					// Simple case, signaling server has a connection to the same endpoint
+					subscriber, err := conn.newSubscriber(ctx, listener, id, publisher, streamType)
+					if err != nil {
+						log.Printf("Could not create subscriber for %s publisher %s: %s", streamType, publisher, err)
+						return
+					}
+
+					ch <- subscriber
+					return
+				}
+
+				// TODO: Create temporary connection to new proxy and tear down when last subscriber left.
+				log.Printf("Not implemented yet: need new connection to %s (%s) for %s publisher %s (%s)", url, ip, streamType, publisher, id)
+			}(client)
+		}
+	}
+
+	select {
+	case subscriber := <-ch:
+		return subscriber, nil
+	case <-ctx.Done():
+		return nil, fmt.Errorf("No %s publisher %s found", streamType, publisher)
+	}
 }
diff --git a/roomsessions.go b/roomsessions.go
index 2bf15bc..cb2c1f1 100644
--- a/roomsessions.go
+++ b/roomsessions.go
@@ -22,6 +22,7 @@
 package signaling
 
 import (
+	"context"
 	"fmt"
 )
 
@@ -34,4 +35,5 @@ type RoomSessions interface {
 	DeleteRoomSession(session Session)
 
 	GetSessionId(roomSessionId string) (string, error)
+	LookupSessionId(ctx context.Context, roomSessionId string) (string, error)
 }
diff --git a/roomsessions_builtin.go b/roomsessions_builtin.go
index 7b65947..3c85984 100644
--- a/roomsessions_builtin.go
+++ b/roomsessions_builtin.go
@@ -22,19 +22,27 @@
 package signaling
 
 import (
+	"context"
+	"errors"
+	"log"
 	"sync"
+	"sync/atomic"
 )
 
 type BuiltinRoomSessions struct {
 	sessionIdToRoomSession map[string]string
 	roomSessionToSessionid map[string]string
 	mu                     sync.RWMutex
+
+	clients *GrpcClients
 }
 
-func NewBuiltinRoomSessions() (RoomSessions, error) {
+func NewBuiltinRoomSessions(clients *GrpcClients) (RoomSessions, error) {
 	return &BuiltinRoomSessions{
 		sessionIdToRoomSession: make(map[string]string),
 		roomSessionToSessionid: make(map[string]string),
+
+		clients: clients,
 	}, nil
 }
 
@@ -78,3 +86,53 @@ func (r *BuiltinRoomSessions) GetSessionId(roomSessionId string) (string, error)
 
 	return sid, nil
 }
+
+func (r *BuiltinRoomSessions) LookupSessionId(ctx context.Context, roomSessionId string) (string, error) {
+	sid, err := r.GetSessionId(roomSessionId)
+	if err == nil {
+		return sid, nil
+	}
+
+	if r.clients == nil {
+		return "", ErrNoSuchRoomSession
+	}
+
+	clients := r.clients.GetClients()
+	if len(clients) == 0 {
+		return "", ErrNoSuchRoomSession
+	}
+
+	lookupctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	var wg sync.WaitGroup
+	var result atomic.Value
+	for _, client := range clients {
+		wg.Add(1)
+		go func(client *GrpcClient) {
+			defer wg.Done()
+
+			sid, err := client.LookupSessionId(lookupctx, roomSessionId)
+			if errors.Is(err, context.Canceled) {
+				return
+			} else if err != nil {
+				log.Printf("Received error while checking for room session id %s on %s: %s", roomSessionId, client.Target(), err)
+				return
+			} else if sid == "" {
+				log.Printf("Received empty session id for room session id %s from %s", roomSessionId, client.Target())
+				return
+			}
+
+			cancel() // Cancel pending RPC calls.
+			result.Store(sid)
+		}(client)
+	}
+	wg.Wait()
+
+	value := result.Load()
+	if value == nil {
+		return "", ErrNoSuchRoomSession
+	}
+
+	return value.(string), nil
+}
diff --git a/roomsessions_builtin_test.go b/roomsessions_builtin_test.go
index 6f212b1..db1394c 100644
--- a/roomsessions_builtin_test.go
+++ b/roomsessions_builtin_test.go
@@ -26,7 +26,7 @@ import (
 )
 
 func TestBuiltinRoomSessions(t *testing.T) {
-	sessions, err := NewBuiltinRoomSessions()
+	sessions, err := NewBuiltinRoomSessions(nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/server.conf.in b/server.conf.in
index 7542a55..acf3bed 100644
--- a/server.conf.in
+++ b/server.conf.in
@@ -234,3 +234,11 @@ connectionsperhost = 8
 #clientkey = /path/to/etcd-client.key
 #clientcert = /path/to/etcd-client.crt
 #cacert = /path/to/etcd-ca.crt
+
+[grpc]
+# IP and port to listen on for GRPC requests.
+# Comment line to disable the listener.
+#listen = 0.0.0.0:9090
+
+# Comma-separated list of GRPC targets to connect to for clustering mode.
+#targets = 192.168.0.1:9090, 192.168.0.1:9091
diff --git a/server/main.go b/server/main.go
index 46fa2b6..ec9d84f 100644
--- a/server/main.go
+++ b/server/main.go
@@ -164,8 +164,14 @@ func main() {
 		}
 	}()
 
+	rpcClients, err := signaling.NewGrpcClients(config)
+	if err != nil {
+		log.Fatalf("Could not create RPC clients: %s", err)
+	}
+	defer rpcClients.Close()
+
 	r := mux.NewRouter()
-	hub, err := signaling.NewHub(config, events, r, version)
+	hub, err := signaling.NewHub(config, events, rpcClients, r, version)
 	if err != nil {
 		log.Fatal("Could not create hub: ", err)
 	}
@@ -192,7 +198,7 @@ func main() {
 				signaling.UnregisterProxyMcuStats()
 				signaling.RegisterJanusMcuStats()
 			case signaling.McuTypeProxy:
-				mcu, err = signaling.NewMcuProxy(config, etcdClient)
+				mcu, err = signaling.NewMcuProxy(config, etcdClient, rpcClients)
 				signaling.UnregisterJanusMcuStats()
 				signaling.RegisterProxyMcuStats()
 			default: