增加socket操作代码

lib/im/SocketClient.dart

@@ -41,6 +41,9 @@ class SocketClient {
   }
 
   authRequest(String token) {
+    if (!checkSocket()) {
+      return;
+    }
     final authReq = AuthReq()
       ..uid = 1
       ..token = '123456';
@@ -51,10 +54,21 @@ class SocketClient {
   }
 
   sendMessage(var to, String content) {
+    if (!checkSocket()) {
+      return;
+    }
     Uint8List data = utf8.encode(content);
     MsgData msgData = MsgData(to: to,from: 2,type: MsgType.SINGLE_TEXT,data: data);
     final proto2 = Proto(5,1,msgData.writeToBuffer());
     _socket.add(proto2.toBytes());
   }
 
+  checkSocket() {
+    if (_socket == null) {
+      connect();
+      return false;
+    }
+    return true;
+  }
+
 }