fixed

change name
     Server -> OverflowApiServer

pom.xml

@@ -22,6 +22,19 @@
         <protoc-maven-plugin.version>0.5.0</protoc-maven-plugin.version>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-protobuf</artifactId>
+            <version>${grpc.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-stub</artifactId>
+            <version>${grpc.version}</version>
+        </dependency>
+    </dependencies>
+
     <build>
         <resources>
             <resource>

src/main/proto/server_grpc.proto

@@ -20,7 +20,7 @@ message ServerOutput {
     string result = 1;
 }
 
-service Server {
+service OverflowApiServer {
     rpc exec(ServerInput) returns (ServerOutput) {}
 }