Trying to send png file from java client to python server

[Rahul Miryala]

Hi All,

Kind request to all of you to help me in sorting out my problem.

I have defined a message proto file for sending the png file from java client to python server. Am able to launch python server correctly and running the java client program to send it but am ending up with no result and

there is no error message also appears to find out the cause.

Posting the code here. Please help me out in finding out the cause.

syntax = "proto3";

service FileServer {

  rpc upload(stream Chunk) returns (Reply) {}

}

message Chunk {

  bytes buffer = 1;

}

message Reply {

  int32 length = 1;

}

Generated the stubs on both python and java sides.

import os

from concurrent import futures

import grpc

import time

import file_upload_pb2, file_upload_pb2_grpc

CHUNK_SIZE = 1024 * 1024  # 1MB

def get_file_chunks(filename):

    with open(filename, 'rb') as f:

        while True:

            piece = f.read(CHUNK_SIZE);

            if len(piece) == 0:

                return

            yield chunk_pb2.Chunk(buffer=piece)

def save_chunks_to_file(chunks, filename):

    with open(filename, 'wb') as f:

        for chunk in chunks:

            f.write(chunk.buffer)

class FileServer(file_upload_pb2_grpc.FileServerServicer):

    def __init__(self):

        print("in Filervser")

        class Servicer(file_upload_pb2_grpc.FileServerServicer):

            def __init__(self):

                print("in service")

                self.tmp_file_name = 'stupid.poto'

            def upload(self, request_iterator, context):

                print("in upload")

                save_chunks_to_file(request_iterator, self.tmp_file_name)

                return file_upload_pb2.Reply(length=os.path.getsize(self.tmp_file_name))

        print("in server")

        self.server = grpc.server(futures.ThreadPoolExecutor(max_workers=1))

        file_upload_pb2_grpc.add_FileServerServicer_to_server(Servicer(), self.server)

    def start(self, port):

        print("starting")

        self.server.add_insecure_port(f'[::]:{port}')

        self.server.start()

        try:

            while True:

                time.sleep(60*60*24)

        except KeyboardInterrupt:

            self.server.stop(0)

if __name__ == '__main__':

    FileServer().start(8888)

Java file

package test.fileupload;

import io.grpc.ManagedChannel;

import io.grpc.ManagedChannelBuilder;

import io.grpc.stub.StreamObserver;

import java.io.BufferedInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.util.logging.Logger;

import com.google.protobuf.ByteString;

import test.fileupload.FileUpload.Reply;

import test.fileupload.FileUpload.Chunk;

public class FileUploadClient {

public static void main(String[] args) {

ManagedChannel mChannel= ManagedChannelBuilder.forAddress("localhost", 8888)

.usePlaintext().build();

FileServerGrpc.FileServerStub fileServerStub = FileServerGrpc.newStub(mChannel);

StreamObserver<Reply> streamReply = new StreamObserver<Reply>() {

@Override

public void onNext(Reply value) {

Logger.getAnonymousLogger().info("on Next");

}

@Override

public void onError(Throwable t) {

Logger.getAnonymousLogger().info("on Error");

}

@Override

public void onCompleted() {

Logger.getAnonymousLogger().info("on Completed");

}

};

StreamObserver<Chunk> chunkStream =fileServerStub.upload(streamReply);

try {

File file = new File("resizedCat.png");

if (file.exists() == false) {

Logger.getAnonymousLogger().info("File does not exist");

return;

}

BufferedInputStream bInputStream = new BufferedInputStream(new FileInputStream(file));

int bufferSize = 1024 * 1024; // 512k

byte[] buffer = new byte[bufferSize];

int tmp = 0;

int size = 0;

while ((tmp = bInputStream.read(buffer)) > 0) {

size += tmp;

ByteString byteString = ByteString.copyFrom(buffer);

Chunk req = Chunk.newBuilder().setBuffer(byteString).build();

chunkStream.onNext(req); 

}

}catch (Exception e) {

Logger.getAnonymousLogger().info("Exception"+e.getMessage());

}

chunkStream.onCompleted();

}

}

[ericgr...@google.com]

Hi,

A couple things you can do to try to narrow down the problem:

(1) A lack of output from the Java client indicates that the connection is (probably) established and perhaps the client is simply waiting for some (potentially non-existent) response from the server. Try setting a short deadline on the client side to verify that nothing is hanging there: See https://grpc.io/blog/deadlines/ for examples of setting a client-side deadline. 

(2) Check if the Python server is working properly without the Java client involved, ideally via grpc_cli (https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md) or else a simple Python client.

Best,

Eric