protobuf是目前应用最广范的设计消息协议工具，具有以下一些特点：
1、proto2只支持python,c++,JAVA,proto3可以支持更多语言
2、定义协议以proto作为文件后缀名，在第一行用syntax指定proto版本
3、C++使用protobuf官方文档：http://developers.google.com/protocol-buffers/docs/cpptutorial当然需要*后才能访问
4、required表示必须字段，optional表示可选字段，在proto3中可以省略定义默认都是可选
5、用protoc生成工具可以直接将proto协议生成对应语言可使用的代码，生成命令比如：protoc --cpp_out=. Protocal.proto
优点：
1、效率和可读性的结合
以下是用protobuf作为通信协议的asio聊天室系统协议部分：
//Protocal.proto
syntax = 'proto3';
message PBindName {
string name = 1;
}
message PChat {
string information = 1;
}
message PRoomInformation {
string name = 1;
string information = 2;
}
生成好该文件后执行protoc --cpp_out=. Protocal.proto可执行.h头文件和.cc代码文件其中需要注意部分：
1、mutable_name()和release_name()分别是获取对string类型的name指针，和释放name指针
2、用的最多的是parsefromstring处理字符串数据
3、用parsefromstream可进行数据流的处理
以下是asio聊天室用protobuf的完整例子：
协议处理部分：
//structHeader.h
#ifndef FND_STRUCT_HEADER_H
#define FND_STRUCT_HEADER_H
#include <string>
struct Header {
int bodySize;
int type;
};
enum MessageType {
MT_BIND_NAME = 1, // {"name" : "abc"}
MT_CHAT_INFO = 2, // {"information" "what i say"}
MT_ROOM_INFO = 3, // {"name" : "abc", "information" : "what i say"}
};
// client send
struct BindName {
char name[32];
int nameLen;
};
// client send
struct ChatInformation {
char information[256];
int infoLen;
};
// serversend
struct RoomInformation {
BindName name;
ChatInformation chat;
};
bool parseMessage(const std::string &input, int *type, std::string &outbuffer);
bool parseMessage2(const std::string &input, int *type, std::string &outbuffer);
bool parseMessage3(const std::string &input, int *type, std::string &outbuffer);
bool parseMessage4(const std::string &input, int *type, std::string &outbuffer);
#endif
//structHeader.cpp
#include "structHeader.h"
#include "SerilizationObject.h"
#include "JsonObject.h"
#include "Protocal.pb.h"
#include <cstdlib>
#include <cstring>
#include <iostream>
template <typename T> std::string seriliaze(const T &obj) {
std::stringstream ss;
boost::archive::text_oarchive oa(ss);
oa & obj;
return ss.str();
}
bool parseMessage4(const std::string &input, int *type,
std::string &outbuffer) {
auto pos = input.find_first_of(" ");
if (pos == std::string::npos)
return false;
if (pos == 0)
return false;
// "BindName ok" -> substr -> BindName
auto command = input.substr(0, pos);
if (command == "BindName") {
// we try to bind name
std::string name = input.substr(pos + 1);
if (name.size() > 32)
return false;
if (type)
*type = MT_BIND_NAME;
PBindName bindName;
bindName.set_name(name);
//auto oldname = bindName.name();
auto ok = bindName.SerializeToString(&outbuffer);
return ok;
} else if (command == "Chat") {
// we try to chat
std::string chat = input.substr(pos + 1);
if (chat.size() > 256)
return false;
PChat pchat;
pchat.set_information(chat);
auto ok = pchat.SerializeToString(&outbuffer);
if (type)
*type = MT_CHAT_INFO;
return ok;
}
return false;
}
bool parseMessage3(const std::string &input, int *type,
std::string &outbuffer) {
auto pos = input.find_first_of(" ");
if (pos == std::string::npos)
return false;
if (pos == 0)
return false;
// "BindName ok" -> substr -> BindName
auto command = input.substr(0, pos);
if (command == "BindName") {
// we try to bind name
std::string name = input.substr(pos + 1);
if (name.size() > 32)
return false;
if (type)
*type = MT_BIND_NAME;
ptree tree;
tree.put("name", name);
outbuffer = ptreeToJsonString(tree);
//outbuffer = seriliaze(SBindName(std::move(name)));
return true;
} else if (command == "Chat") {
// we try to chat
std::string chat = input.substr(pos + 1);
if (chat.size() > 256)
return false;
ptree tree;
tree.put("information", chat);
outbuffer = ptreeToJsonString(tree);
//outbuffer = seriliaze(SChatInfo(std::move(chat)));
if (type)
*type = MT_CHAT_INFO;
return true;
}
return false;
}
bool parseMessage2(const std::string &input, int *type,
std::string &outbuffer) {
auto pos = input.find_first_of(" ");
if (pos == std::string::npos)
return false;
if (pos == 0)
return false;
// "BindName ok" -> substr -> BindName
auto command = input.substr(0, pos);
if (command == "BindName") {
// we try to bind name
std::string name = input.substr(pos + 1);
if (name.size() > 32)
return false;
if (type)
*type = MT_BIND_NAME;
//SBindName bindInfo(std::move(name));
outbuffer = seriliaze(SBindName(std::move(name)));
return true;
} else if (command == "Chat") {
// we try to chat
std::string chat = input.substr(pos + 1);
if (chat.size() > 256)
return false;
outbuffer = seriliaze(SChatInfo(std::move(chat)));
// ChatInformation info;
// info.infoLen = chat.size();
// std::memcpy(&(info.information), chat.data(), chat.size());
// auto buffer = reinterpret_cast<const char *>(&info);
// outbuffer.assign(buffer, buffer + sizeof(info));
if (type)
*type = MT_CHAT_INFO;
return true;
}
return false;
}
// cmd messagebody
bool parseMessage(const std::string &input, int *type, std::string &outbuffer) {
// input should be cmd body
auto pos = input.find_first_of(" ");
if (pos == std::string::npos)
return false;
if (pos == 0)
return false;
// "BindName ok" -> substr -> BindName
auto command = input.substr(0, pos);
if (command == "BindName") {
// we try to bind name
std::string name = input.substr(pos + 1);
if (name.size() > 32)
return false;
if (type)
*type = MT_BIND_NAME;
BindName bindInfo;
bindInfo.nameLen = name.size();
std::memcpy(&(bindInfo.name), name.data(), name.size());
auto buffer = reinterpret_cast<const char *>(&bindInfo);
outbuffer.assign(buffer, buffer + sizeof(bindInfo));
return true;
} else if (command == "Chat") {
// we try to chat
std::string chat = input.substr(pos + 1);
if (chat.size() > 256)
return false;
ChatInformation info;
info.infoLen = chat.size();
std::memcpy(&(info.information), chat.data(), chat.size());
auto buffer = reinterpret_cast<const char *>(&info);
outbuffer.assign(buffer, buffer + sizeof(info));
if (type)
*type = MT_CHAT_INFO;
return true;
}
return false;
}
聊天消息处理：
//chat_message.h
#ifndef CHAT_MESSAGE_HPP
#define CHAT_MESSAGE_HPP
#include "structHeader.h"
#include "SerilizationObject.h"
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
// s -> c c -> s message { header, body } // header length
class chat_message {
public:
enum { header_length = sizeof(Header) };
enum { max_body_length = 512 };
chat_message(){}
const char *data() const { return data_; }
char *data() { return data_; }
std::size_t length() const { return header_length + m_header.bodySize; }
const char *body() const { return data_ + header_length; }
char *body() { return data_ + header_length; }
int type() const { return m_header.type; }
std::size_t body_length() const { return m_header.bodySize; }
void setMessage(int messageType, const void *buffer, size_t bufferSize) {
assert(bufferSize <= max_body_length);
m_header.bodySize = bufferSize;
m_header.type = messageType;
std::memcpy(body(), buffer, bufferSize);
std::memcpy(data(), &m_header, sizeof(m_header));
}
void setMessage(int messageType, const std::string& buffer) {
setMessage(messageType, buffer.data(), buffer.size());
}
bool decode_header() {
std::memcpy(&m_header, data(), header_length);
if (m_header.bodySize > max_body_length) {
std::cout << "body size " << m_header.bodySize << " " << m_header.type
<< std::endl;
return false;
}
return true;
}
private:
char data_[header_length + max_body_length];
Header m_header;
};
#endif // CHAT_MESSAGE_HPP
服务器代码部分：
//main.cpp
#include "chat_message.h"
#include "JsonObject.h"
#include "Protocal.pb.h"
#include <boost/asio.hpp>
#include <deque>
#include <iostream>
#include <list>
#include <memory>
#include <set>
#include <utility>
#include <cstdlib>
using boost::asio::ip::tcp;
//----------------------------------------------------------------------
using chat_message_queue = std::deque<chat_message>;
using chat_message_queue2 = std::list<chat_message>;
//----------------------------------------------------------------------
//----------------------------------------------------------------------
class chat_session;
using chat_session_ptr = std::shared_ptr<chat_session>;
class chat_room {
public:
public:
void join(chat_session_ptr);
void leave(chat_session_ptr);
void deliver(const chat_message&);
private:
std::set<chat_session_ptr> participants_;
enum { max_recent_msgs = 100 };
chat_message_queue recent_msgs_;
};
//----------------------------------------------------------------------
class chat_session : public std::enable_shared_from_this<chat_session> {
public:
chat_session(tcp::socket socket, chat_room &room)
: socket_(std::move(socket)), room_(room) {}
void start() {
room_.join(shared_from_this());
do_read_header();
}
void deliver(const chat_message &msg) {
// first false
bool write_in_progress = !write_msgs_.empty();
write_msgs_.push_back(msg);
if (!write_in_progress) {
// first
do_write();
}
}
private:
void do_read_header() {
auto self(shared_from_this());
boost::asio::async_read(
socket_,
boost::asio::buffer(read_msg_.data(), chat_message::header_length),
[this, self](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec && read_msg_.decode_header()) {
do_read_body();
} else {
std::cout << "Player leave the room\n";
room_.leave(shared_from_this());
}
});
}
void do_read_body() {
auto self(shared_from_this());
boost::asio::async_read(
socket_, boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),
[this, self](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
//room_.deliver(read_msg_);
handleMessage();
do_read_header();
} else {
room_.leave(shared_from_this());
}
});
}
template <typename T> T toObject() {
T obj;
std::stringstream ss(std::string(
read_msg_.body(), read_msg_.body() + read_msg_.body_length()));
boost::archive::text_iarchive oa(ss);
oa &obj;
return obj;
}
bool fillProtobuf(::google::protobuf::Message* msg) {
std::string ss(
read_msg_.body(), read_msg_.body() + read_msg_.body_length());
auto ok = msg->ParseFromString(ss);
return ok;
}
ptree toPtree() {
ptree obj;
std::stringstream ss(
std::string(read_msg_.body(),
read_msg_.body() + read_msg_.body_length()));
boost::property_tree::read_json(ss, obj);
return obj;
}
void handleMessage() {
if (read_msg_.type() == MT_BIND_NAME) {
PBindName bindName;
if(fillProtobuf(&bindName))
m_name = bindName.name();
} else if (read_msg_.type() == MT_CHAT_INFO) {
PChat chat;
if(!fillProtobuf(&chat)) return;
m_chatInformation = chat.information();
auto rinfo = buildRoomInfo();
chat_message msg;
msg.setMessage(MT_ROOM_INFO, rinfo);
room_.deliver(msg);
} else {
// not valid msg do nothing
}
}
void do_write() {
auto self(shared_from_this());
boost::asio::async_write(
socket_, boost::asio::buffer(write_msgs_.front().data(),
write_msgs_.front().length()),
[this, self](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
write_msgs_.pop_front();
if (!write_msgs_.empty()) {
do_write();
}
} else {
room_.leave(shared_from_this());
}
});
}
tcp::socket socket_;
chat_room &room_;
chat_message read_msg_;
chat_message_queue write_msgs_;
std::string m_name;
std::string m_chatInformation;
std::string buildRoomInfo() const {
PRoomInformation roomInfo;
roomInfo.set_name(m_name);
roomInfo.set_information(m_chatInformation);
std::string out;
auto ok = roomInfo.SerializeToString(&out);
assert(ok);
return out;
}
// RoomInformation buildRoomInfo() const {
// RoomInformation info;
// info.name.nameLen = m_name.size();
// std::memcpy(info.name.name, m_name.data(), m_name.size());
// info.chat.infoLen = m_chatInformation.size();
// std::memcpy(info.chat.information, m_chatInformation.data(),
// m_chatInformation.size());
// return info;
// }
};
void chat_room::join(chat_session_ptr participant) {
participants_.insert(participant);
for (const auto& msg : recent_msgs_)
participant->deliver(msg);
}
void chat_room::leave(chat_session_ptr participant) {
participants_.erase(participant);
}
void chat_room::deliver(const chat_message &msg) {
recent_msgs_.push_back(msg);
while (recent_msgs_.size() > max_recent_msgs)
recent_msgs_.pop_front();
for (auto& participant : participants_)
participant->deliver(msg);
}
//----------------------------------------------------------------------
class chat_server {
public:
chat_server(boost::asio::io_service &io_service,
const tcp::endpoint &endpoint)
: acceptor_(io_service, endpoint), socket_(io_service) {
do_accept();
}
private:
void do_accept() {
acceptor_.async_accept(socket_, [this](boost::system::error_code ec) {
if (!ec) {
auto session =
std::make_shared<chat_session>(std::move(socket_), room_);
session->start();
}
do_accept();
});
}
tcp::acceptor acceptor_;
tcp::socket socket_;
chat_room room_;
};
//----------------------------------------------------------------------
int main(int argc, char *argv[]) {
try {
GOOGLE_PROTOBUF_VERIFY_VERSION;
if (argc < 2) {
std::cerr << "Usage: chat_server <port> [<port> ...]\n";
return 1;
}
boost::asio::io_service io_service;
std::list<chat_server> servers;
for (int i = 1; i < argc; ++i) {
tcp::endpoint endpoint(tcp::v4(), std::atoi(argv[i]));
servers.emplace_back(io_service, endpoint);
}
io_service.run();
} catch (std::exception &e) {
std::cerr << "Exception: " << e.what() << "\n";
}
google::protobuf::ShutdownProtobufLibrary();
return 0;
}
客户端代码部分：
//client.cpp
#include "chat_message.h"
#include "structHeader.h"
#include "JsonObject.h"
#include "SerilizationObject.h"
#include "Protocal.pb.h"
#include <boost/asio.hpp>
#include <deque>
#include <iostream>
#include <thread>
#include <cstdlib>
#include <cassert>
using boost::asio::ip::tcp;
using chat_message_queue = std::deque<chat_message>;
class chat_client {
public:
chat_client(boost::asio::io_service &io_service,
tcp::resolver::iterator endpoint_iterator)
: io_service_(io_service), socket_(io_service) {
do_connect(endpoint_iterator);
}
void write(const chat_message &msg) {
io_service_.post([this, msg]() {
bool write_in_progress = !write_msgs_.empty();
write_msgs_.push_back(msg);
if (!write_in_progress) {
do_write();
}
});
}
void close() {
io_service_.post([this]() { socket_.close(); });
}
private:
void do_connect(tcp::resolver::iterator endpoint_iterator) {
boost::asio::async_connect(
socket_, endpoint_iterator,
[this](boost::system::error_code ec, tcp::resolver::iterator) {
if (!ec) {
do_read_header();
}
});
}
void do_read_header() {
boost::asio::async_read(
socket_,
boost::asio::buffer(read_msg_.data(), chat_message::header_length),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec && read_msg_.decode_header()) {
do_read_body();
} else {
socket_.close();
}
});
}
void do_read_body() {
boost::asio::async_read(
socket_, boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
if (read_msg_.type() == MT_ROOM_INFO) {
//SRoomInfo info;
std::string buffer(read_msg_.body(),
read_msg_.body() + read_msg_.body_length());
PRoomInformation roomInfo;
auto ok = roomInfo.ParseFromString(buffer);
//if(!ok) throw std::runtime_error("not valid message");
//std::stringstream ss(buffer);
//ptree tree;
//boost::property_tree::read_json(ss, tree);
if (ok) {
std::cout << "client: '";
std::cout << roomInfo.name();
std::cout << "' says '";
std::cout
<< roomInfo.information();
std::cout << "'\n";
}
// boost::archive::text_iarchive ia(ss);
// ia & info;
// std::cout << "client: '";
// std::cout << info.name();
// std::cout << "' says '";
// std::cout << info.information();
// std::cout << "'\n";
}
do_read_header();
} else {
socket_.close();
}
});
}
void do_write() {
boost::asio::async_write(
socket_, boost::asio::buffer(write_msgs_.front().data(),
write_msgs_.front().length()),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
write_msgs_.pop_front();
if (!write_msgs_.empty()) {
do_write();
}
} else {
socket_.close();
}
});
}
private:
boost::asio::io_service &io_service_;
tcp::socket socket_;
chat_message read_msg_;
chat_message_queue write_msgs_;
};
int main(int argc, char *argv[]) {
try {
GOOGLE_PROTOBUF_VERIFY_VERSION;
if (argc != 3) {
std::cerr << "Usage: chat_client <host> <port>\n";
return 1;
}
boost::asio::io_service io_service;
tcp::resolver resolver(io_service);
auto endpoint_iterator = resolver.resolve({argv[1], argv[2]});
chat_client c(io_service, endpoint_iterator);
std::thread t([&io_service]() { io_service.run(); });
char line[chat_message::max_body_length + 1];
// ctrl-d
while (std::cin.getline(line, chat_message::max_body_length + 1)) {
chat_message msg;
auto type = 0;
std::string input(line, line + std::strlen(line));
std::string output;
if(parseMessage4(input, &type, output)) {
msg.setMessage(type, output.data(), output.size());
c.write(msg);
std::cout << "write message for server " << output.size() << std::endl;
}
}
c.close();
t.join();
} catch (std::exception &e) {
std::cerr << "Exception: " << e.what() << "\n";
}
google::protobuf::ShutdownProtobufLibrary();
return 0;
}