--- /dev/null
+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+typedef NS_ENUM(NSUInteger, FIRMessagingSecureSocketState){
+ kFIRMessagingSecureSocketNotOpen = 0,
+ kFIRMessagingSecureSocketOpening,
+ kFIRMessagingSecureSocketOpen,
+ kFIRMessagingSecureSocketClosing,
+ kFIRMessagingSecureSocketClosed,
+ kFIRMessagingSecureSocketError
+};
+
+@class FIRMessagingSecureSocket;
+
+@protocol FIRMessagingSecureSocketDelegate<NSObject>
+
+- (void)secureSocket:(FIRMessagingSecureSocket *)socket
+ didReceiveData:(NSData *)data
+ withTag:(int8_t)tag;
+- (void)secureSocket:(FIRMessagingSecureSocket *)socket
+ didSendProtoWithTag:(int8_t)tag
+ rmqId:(NSString *)rmqId;
+- (void)secureSocketDidConnect:(FIRMessagingSecureSocket *)socket;
+- (void)didDisconnectWithSecureSocket:(FIRMessagingSecureSocket *)socket;
+
+@end
+
+/**
+ * This manages the input/output streams connected to the MCS server. Used to receive data from
+ * the server and send to it over the wire.
+ */
+@interface FIRMessagingSecureSocket : NSObject
+
+@property(nonatomic, readwrite, weak) id<FIRMessagingSecureSocketDelegate> delegate;
+@property(nonatomic, readonly, assign) FIRMessagingSecureSocketState state;
+
+- (void)connectToHost:(NSString *)host port:(NSUInteger)port onRunLoop:(NSRunLoop *)runLoop;
+- (void)disconnect;
+- (void)sendData:(NSData *)data withTag:(int8_t)tag rmqId:(NSString *)rmqId;
+
+@end