Grpc-java: First received frame was not SETTINGS. Hex dump for first 5 bytes: 1503010002

[yuzheng21]

Please answer these questions before submitting your issue.

What version of gRPC are you using?

1.6.1

What JVM are you using (java -version)?
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

What did you do?

I ran a grpc server (in Golang) and a client (in Java) that accessed this server.
The error occurred always when I tried to send request to server via a blockingStub

blockingStub = AgentGrpc.newBlockingStub(ManagedChannelBuilder.forAddress(host, port).usePlaintext(true).build());

What did you expect to see?

Successful call

What did you see instead?

io.grpc.StatusRuntimeException: INTERNAL
    at io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:210)
    at io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:191)
    at io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:124)
    at com.ibm.watson.serve.agent.AgentGrpc$AgentBlockingStub.pushServerStatus(AgentGrpc.java:281)
    at com.ibm.watson.model_serving.AgentClient.sendServerStatus(AgentClient.java:32)
    at com.ibm.watson.model_serving.ServerExample$ServerExampleService.addModel(ServerExample.java:463)
    at com.ibm.watson.serve.runtime.ServiceRuntimeGrpc$MethodHandlers.invoke(ServiceRuntimeGrpc.java:593)
    at io.grpc.stub.ServerCalls$UnaryServerCallHandler$UnaryServerCallListener.onHalfClose(ServerCalls.java:174)
    at io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.halfClosed(ServerCallImpl.java:272)
    at io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$2.runInContext(ServerImpl.java:594)
    at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
    at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:102)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: io.netty.handler.codec.http2.Http2Exception: First received frame was not SETTINGS. Hex dump for first 5 bytes: 1503010002
    at io.netty.handler.codec.http2.Http2Exception.connectionError(Http2Exception.java:85)
    at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.verifyFirstFrameIsSettings(Http2ConnectionHandler.java:321)
    at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.decode(Http2ConnectionHandler.java:222)
    at io.netty.handler.codec.http2.Http2ConnectionHandler.decode(Http2ConnectionHandler.java:414)
    at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1342)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:934)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:645)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:580)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:497)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:459)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
    at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)
    ... 1 more

[carl-mastrangelo]

This is usually because the server is using SSL, but the client is not.

You should avoid using plaintext.

[yuzheng21]

@carl-mastrangelo yeah, I just found the mistake. thanks!