将 protobuf 从 C++ 发送到 Java

Question

我正在尝试通过套接字将 protobuf 从 C++ 应用程序发送到 Java 应用程序。我在 mu C++ 程序上使用一个简单的套接字来发送 protobuf。在通过网络发送它之前，我已经将它序列化为一个字符缓冲区。在我的 Java(server) 程序中，我使用 ServerSocket 来接收数据。

我在 Java 端反序列化 protobuf 时遇到问题。它一直给我错误：

解析协议消息时，输入在字段中间意外结束。这可能意味着输入已被截断或嵌入的消息错误报告了自己的长度。
CodedInputStream 遇到格式错误的 varint。

我做错了什么？我的代码如下。

protobuf 示例取自 Google 的教程 - AddressBook.proto 教程

C++代码：

#define WIN32_LEAN_AND_MEAN
#include <iostream>
#include <fstream>
#include <string>   
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include<conio.h>
#include "addressbook.pb.h"

#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")

using namespace std;

// This function fills in a Person message based on user input.
void PromptForAddress(tutorial::Person* person) {
    cout << "Enter person ID number: ";
    int id;
    cin >> id;
    person->set_id(id);
    cin.ignore(256, '\n');

    cout << "Enter name: ";
    getline(cin, *person->mutable_name());

    cout << "Enter email address (blank for none): ";
    string email;
    getline(cin, email);
    if (!email.empty()) {
        person->set_email(email);
    }

    while (true) {
        cout << "Enter a phone number (or leave blank to finish): ";
        string number;
        getline(cin, number);
        if (number.empty()) {
            break;
        }

        tutorial::Person::PhoneNumber* phone_number = person->add_phone();
        phone_number->set_number(number);

        cout << "Is this a mobile, home, or work phone? ";
        string type;
        getline(cin, type);
        if (type == "mobile") {
            phone_number->set_type(tutorial::Person::MOBILE);
        }
        else if (type == "home") {
            phone_number->set_type(tutorial::Person::HOME);
        }
        else if (type == "work") {
            phone_number->set_type(tutorial::Person::WORK);
        }
        else {
            cout << "Unknown phone type.  Using default." << endl;
        }
    }
}

// Main function:  Reads the entire address book from a file,
//   adds one person based on user input, then writes it back out to the same
//   file.
int main(int argc, char* argv[]) {
    // Verify that the version of the library that we linked against is
    // compatible with the version of the headers we compiled against.
    GOOGLE_PROTOBUF_VERIFY_VERSION;

    tutorial::AddressBook address_book;


    // Add an address.
    PromptForAddress(address_book.add_person());

    {
        int size = address_book.ByteSize();
        char * buffer = new char[size];
        address_book.SerializeToArray(buffer, size);

        WSADATA wsaData;
        SOCKET ConnectSocket = INVALID_SOCKET;
        struct addrinfo *result = NULL,
                *ptr = NULL,
                hints;
        int iResult;

        // Initialize Winsock
        iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);

        ZeroMemory(&hints, sizeof(hints));
        hints.ai_family = AF_UNSPEC;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_protocol = IPPROTO_TCP;

        // Resolve the server address and port
        iResult = getaddrinfo("localhost", "5000", &hints, &result);
        if (iResult != 0) {
            printf("getaddrinfo failed with error: %d\n", iResult);
            WSACleanup();
            return 1;
        }

        // Attempt to connect to an address until one succeeds
        for (ptr = result; ptr != NULL; ptr = ptr->ai_next) 
        {

            // Create a SOCKET for connecting to server
            ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
                    ptr->ai_protocol);

            // Connect to server.
            iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
            if (iResult == SOCKET_ERROR) {
                closesocket(ConnectSocket);
                ConnectSocket = INVALID_SOCKET;
                continue;
            }
            freeaddrinfo(result);

            // Send an initial buffer
            iResult = send(ConnectSocket, buffer, (int)strlen(buffer), 0);
            if (iResult == SOCKET_ERROR) {
                printf("send failed with error: %d\n", WSAGetLastError());
                closesocket(ConnectSocket);
                WSACleanup();
                return 1;
            }
            printf("Bytes Sent: %ld\n", iResult);

            _getch();
            // Optional:  Delete all global objects allocated by libprotobuf.
            google::protobuf::ShutdownProtobufLibrary();

            return 0;
        }
    }
}

Java 程序：

package networkmonitor;

import com.example.tutorial.AddressBookProtos.AddressBook;
import com.example.tutorial.AddressBookProtos.Person;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.Parser;
import java.io.IOException;
import java.io.InputStream;
import static java.lang.System.in;
import java.net.ServerSocket;
import java.net.Socket;

class NetworkMonitor {
    // Iterates though all people in the AddressBook and prints info about them.
    static void Print(AddressBook addressBook) {
        for (Person person: addressBook.getPersonList()) {
            System.out.println("Person ID: " + person.getId());
            System.out.println("  Name: " + person.getName());
            if (person.hasEmail()) {
                System.out.println("  E-mail address: " + person.getEmail());
            }

            for (Person.PhoneNumber phoneNumber : person.getPhoneList()) {
                switch (phoneNumber.getType()) {
                case MOBILE:
                    System.out.print("  Mobile phone #: ");
                    break;
                case HOME:
                    System.out.print("  Home phone #: ");
                    break;
                case WORK:
                    System.out.print("  Work phone #: ");
                    break;
                }
                System.out.println(phoneNumber.getNumber());
            }
        }
    }

    // Main function:  Reads the entire address book from a file and prints all
    //   the information inside.
    public static void main(String[] args) throws Exception {

        ServerSocket server = null;
        try 
        {
            server = new ServerSocket(5000);
        } 
        catch (IOException e) 
        {
            System.out.println("Error on port: 5000 " + ", " + e);
            System.exit(1);
        }

        System.out.println("Server setup and waiting for client connection ...");

        Socket client = null;
        try 
        {
            client = server.accept();
        } 
        catch (IOException e) 
        {
            System.out.println("Did not accept connection: " + e);
            System.exit(1);
        }

        System.out.println("Client connection accepted. Moving to local port     ...");

        try
        {
            InputStream inStream = client.getInputStream();
            AddressBook addressBook = AddressBook.parseDelimitedFrom(inStream);
            Print(addressBook);
            in.close();
            client.close();
            server.close();
        }
        catch(IOException e)
        { System.out.println("IO Error in streams " + e);
        e.printStackTrace();}
    }
}

Answer 1

好的。我阅读了文档。

int size = address_book.ByteSize();
char * buffer = new char[size];
address_book.SerializeToArray(buffer, size);

使用消息的大小构建完整的消息。该消息不是字符串。为了使消息尽可能小，这是一堆乱七八糟的东西。

iResult = send(ConnectSocket, buffer, (int)strlen(buffer), 0);

将消息发送到缓冲区中嵌入的第一个空值或缓冲区之后（如果缓冲区不包含任何空值）。您很可能会发送太多或太少。

幸运的是，您已经知道消息的大小：size。

iResult = send(ConnectSocket, buffer, size, 0);

应该做的。

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