Serializing and Sending a Protocol Buffers Message

Question

I have written this protobuf message in c#

• C# client:

      public AddressBook InitializeAdressBook() { 
  
          Person newContact = new Person();
          AddressBook addressBookBuilder = new  AddressBook();
          Person john = new Person();
          john.id=1234;
          john.name="John Doe";
          john.email="jdoe@example.com";
          Person.PhoneNumber nr = new Person.PhoneNumber();
          nr.number="5554321";
          john.phone.Add(nr);
          addressBookBuilder.person.Add(john);
          TextBox.Text += ("Client: Initialisiert? " + addressBookBuilder.ToString()) + "\t" + "\n";
          TextBox.Text += " Erster Person " + addressBookBuilder.person.First().name + "\t" + "\n";
  
          return addressBookBuilder;
      }
  

Problem

I am trying to send a protobuf message from a c# client to this java server...

• Java server

  public ControllerThread(Socket s){
  this.s = s; 
  try {
          AddressBook adb = AddressBook.parseFrom(s.getInputStream());
          System.out.println("Server: Addressbook:" + adb.getPersonCount());
  
      } catch (IOException e) { 
          System.out.println("Server: BufferedReader oder PrintWriter von ThermoClient konnte nicht erstellt werden");
          e.printStackTrace(); } 
      } 
  

  }

Question:

I should serialize this message to a byte array, so that i can send it to the java server... Unfortunately the method ProtoBuf.Serializer.Serialize dont return a byte array back. So how can i serialize it as a byte array and send it to my Java Server? Any help appreciated thanks!

Answer 1

protobuf-net (aka ProtoBuf.Serializer.Serialize) writes to streams. If you have the socket available as a NetworkStream, you can just write directly to that. If you really want a byte[], then use MemoryStream:

byte[] data;
using(var ms = new MemoryStream()) {
     Serializer.Serialize(ms, obj);
     data = ms.ToArray();
}

Answer 2

First you had better double check the protocol of the Java server. As described here protobuf is not self-delimiting. This means if you have a TCP connection and are sending multiple protobuf messages, there must be some other underlying protocol to take care of framing - determining where one message ends and another begins.

Let's ignore that problem for now. The actual code to serialize the message depends on which C#/protobuf library you are using. If you are using Jon Skeet's protobuf-csharp-port you might serialize it this way:

AddressBook book = InitializeAddressBook();
byte[] bookBytes = book.ToByteArray();

bookBytes is the address book, serialized to a byte array. Then use whatever socket library you want (for example TcpClient) to send the data (bookBytes) to the Java server.

I'm not convinced this will work because I think there are details about the Java server that you are not telling us.