Chunker.py

##### server.py start #####
from concurrent import futures
import time
import logging

import grpc

import chunker_pb2
import chunker_pb2_grpc

_ONE_DAY_IN_SECONDS = 60 * 60 * 24
_CHUNKER_SIZE = 4
_DATA_TO_SEND = 'Hello gRPC Python World!'

def _chunk_bytes(data, chunker_size):
    index = 0
    while index < len(data):
        yield chunker_pb2.Chunk(
            chunk=data[index:index+chunker_size]
        )
        index += chunker_size


class Chunker(chunker_pb2_grpc.ChunkerServicer):

    @staticmethod
    def Chunker(request, unused_context):
        return _chunk_bytes(
            _DATA_TO_SEND,
            _CHUNKER_SIZE)


def serve():
    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
    chunker_pb2_grpc.add_ChunkerServicer_to_server(Chunker(), server)
    server.add_insecure_port('[::]:50051')
    server.start()
    try:
        while True:
            time.sleep(_ONE_DAY_IN_SECONDS)
    except KeyboardInterrupt:
        server.stop(0)


if __name__ == '__main__':
    logging.basicConfig()
    serve()
##### server.py end #####


##### client.py start #####from __future__ import print_function
import logging

from google.protobuf import empty_pb2
import grpc

import chunker_pb2
import chunker_pb2_grpc


def run():
    # NOTE(gRPC Python Team): .close() is possible on a channel and should be
    # used in circumstances in which the with statement does not fit the needs
    # of the code.
    with grpc.insecure_channel('localhost:50051') as channel:
        stub = chunker_pb2_grpc.ChunkerStub(channel)
        try:
            response_iterator = stub.Chunker(empty_pb2.Empty())
            received_bytes = bytes()
            for response in response_iterator:
                received_bytes += response.chunk
                print('Received %d bytes...', len(response.chunk))
        except grpc.RpcError as rpc_error:
            print('Handle exception here...')
            raise rpc_error
    print('Concatenated Response:')
    print(received_bytes)


if __name__ == '__main__':
    logging.basicConfig()
    run()
##### client.py end #####

Program doesn't execute. You need to convert string within _DATA_TO_SEND to bytes before chunking as chunker_pb2.Chunk is expecting bytes not str.

_DATA_TO_SEND = b'Hello gRPC Python World!'