linux C++中套接字上的协议缓冲区

nue99wik  于 2023-08-03  发布在  Linux
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我正在尝试探索Linux平台下的协议缓冲区（PB），我的编码语言是C++。我在protocol buffer online docs中找到了示例，但没有任何特定于socket send和receive的示例（或者我完全错过了：））。所以我决定在实际消息之前添加消息长度，并通过套接字发送它。我会很感激，如果任何人可以建议一个更好的解决方案比我计划做的，也有什么准备在PB创建这样的数据包。
但是我仍然在服务器端遇到了一个问题，我必须解码数据包。假设客户端发送10字节的分组，其中前4字节是分组的长度;但是在解码分组之前不可能知道长度。因此，即使我读取了前4个字节，我如何使用协议缓冲区推导出半读数据包的值。

linux

2条答案

按热度按时间
f87krz0w

f87krz0w1#

我终于可以让它工作了。我在这里发布代码，以便人们可以审查和评论它，以及如果有人想在c++中实现它，这段代码可以帮助。这是一个破旧的代码，我的意图是让Protobuf工作在长度前缀的方式。我已经采取了一些网站，我不记得客户端服务器的代码，我已经修改它，以适应protobuf。在这里，服务器首先查看套接字并获取总数据包的长度，然后执行实际的套接字读取以读取整个数据包。有无数种方法可以做到这一点，但为了快速解决，我这样做了。但是我需要找到一个更好的方法来避免每个包2个recv，但是在我的条件下所有的消息都是不同大小的，所以这是我猜测的唯一方法。
原文件

message log_packet {
  required fixed64 log_time =1;
  required fixed32 log_micro_sec =2;
  required fixed32 sequence_no =3;
  required fixed32 shm_app_id =4;
  required string packet_id =5;
  required string log_level=6;
  required string log_msg=7;
  }

字符串
协议缓冲区客户端代码

#include <unistd.h>
#include "message.pb.h"
#include <iostream>
#include <google/protobuf/message.h>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/io/zero_copy_stream_impl.h>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/io/zero_copy_stream_impl_lite.h>

using namespace google::protobuf::io;

using namespace std;
int main(int argv, char** argc){

/* Coded output stram */

log_packet payload ;

payload.set_log_time(10);
payload.set_log_micro_sec(10);
payload.set_sequence_no(1);
payload.set_shm_app_id(101);
payload.set_packet_id("TST");
payload.set_log_level("DEBUG");
payload.set_log_msg("What shall we say then");

cout<<"size after serilizing is "<<payload.ByteSize()<<endl;
int siz = payload.ByteSize()+4;
char *pkt = new char [siz];
google::protobuf::io::ArrayOutputStream aos(pkt,siz);
CodedOutputStream *coded_output = new CodedOutputStream(&aos);
coded_output->WriteVarint32(payload.ByteSize());
payload.SerializeToCodedStream(coded_output);

        int host_port= 1101;
        char* host_name="127.0.0.1";

        struct sockaddr_in my_addr;

        char buffer[1024];
        int bytecount;
        int buffer_len=0;

        int hsock;
        int * p_int;
        int err;

        hsock = socket(AF_INET, SOCK_STREAM, 0);
        if(hsock == -1){
                printf("Error initializing socket %d\n",errno);
                goto FINISH;
        }

        p_int = (int*)malloc(sizeof(int));
        *p_int = 1;

        if( (setsockopt(hsock, SOL_SOCKET, SO_REUSEADDR, (char*)p_int, sizeof(int)) == -1 )||
                (setsockopt(hsock, SOL_SOCKET, SO_KEEPALIVE, (char*)p_int, sizeof(int)) == -1 ) ){
                printf("Error setting options %d\n",errno);
                free(p_int);
                goto FINISH;
        }
        free(p_int);

        my_addr.sin_family = AF_INET ;
        my_addr.sin_port = htons(host_port);

        memset(&(my_addr.sin_zero), 0, 8);
        my_addr.sin_addr.s_addr = inet_addr(host_name);
        if( connect( hsock, (struct sockaddr*)&my_addr, sizeof(my_addr)) == -1 ){
                if((err = errno) != EINPROGRESS){
                        fprintf(stderr, "Error connecting socket %d\n", errno);
                        goto FINISH;
                }
        }



       for (int i =0;i<10000;i++){
          for (int j = 0 ;j<10;j++) {

                if( (bytecount=send(hsock, (void *) pkt,siz,0))== -1 ) {
                        fprintf(stderr, "Error sending data %d\n", errno);
                        goto FINISH;
                }
                printf("Sent bytes %d\n", bytecount);
                usleep(1);
         }
        }
        delete pkt;

FINISH:
        close(hsock);

}

型
协议缓冲区服务器代码

#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <netinet/in.h>
#include <resolv.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
#include "message.pb.h"
#include <iostream>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/io/zero_copy_stream_impl.h>

using namespace std;
using namespace google::protobuf::io;


void* SocketHandler(void*);

int main(int argv, char** argc){

        int host_port= 1101;

        struct sockaddr_in my_addr;

        int hsock;
        int * p_int ;
        int err;

        socklen_t addr_size = 0;
        int* csock;
        sockaddr_in sadr;
        pthread_t thread_id=0;

        hsock = socket(AF_INET, SOCK_STREAM, 0);
        if(hsock == -1){
                printf("Error initializing socket %d\n", errno);
                goto FINISH;
        }

        p_int = (int*)malloc(sizeof(int));
        *p_int = 1;

        if( (setsockopt(hsock, SOL_SOCKET, SO_REUSEADDR, (char*)p_int, sizeof(int)) == -1 )||
                (setsockopt(hsock, SOL_SOCKET, SO_KEEPALIVE, (char*)p_int, sizeof(int)) == -1 ) ){
                printf("Error setting options %d\n", errno);
                free(p_int);
                goto FINISH;
        }
        free(p_int);

        my_addr.sin_family = AF_INET ;
        my_addr.sin_port = htons(host_port);

        memset(&(my_addr.sin_zero), 0, 8);
        my_addr.sin_addr.s_addr = INADDR_ANY ;

        if( bind( hsock, (sockaddr*)&my_addr, sizeof(my_addr)) == -1 ){
                fprintf(stderr,"Error binding to socket, make sure nothing else is listening on this port %d\n",errno);
                goto FINISH;
        }
        if(listen( hsock, 10) == -1 ){
                fprintf(stderr, "Error listening %d\n",errno);
                goto FINISH;
        }

        //Now lets do the server stuff

        addr_size = sizeof(sockaddr_in);

        while(true){
                printf("waiting for a connection\n");
                csock = (int*)malloc(sizeof(int));
                if((*csock = accept( hsock, (sockaddr*)&sadr, &addr_size))!= -1){
                        printf("---------------------\nReceived connection from %s\n",inet_ntoa(sadr.sin_addr));
                        pthread_create(&thread_id,0,&SocketHandler, (void*)csock );
                        pthread_detach(thread_id);
                }
                else{
                        fprintf(stderr, "Error accepting %d\n", errno);
                }
        }

FINISH:
;//oops
}

google::protobuf::uint32 readHdr(char *buf)
{
  google::protobuf::uint32 size;
  google::protobuf::io::ArrayInputStream ais(buf,4);
  CodedInputStream coded_input(&ais);
  coded_input.ReadVarint32(&size);//Decode the HDR and get the size
  cout<<"size of payload is "<<size<<endl;
  return size;
}

void readBody(int csock,google::protobuf::uint32 siz)
{
  int bytecount;
  log_packet payload;
  char buffer [siz+4];//size of the payload and hdr
  //Read the entire buffer including the hdr
  if((bytecount = recv(csock, (void *)buffer, 4+siz, MSG_WAITALL))== -1){
                fprintf(stderr, "Error receiving data %d\n", errno);
        }
  cout<<"Second read byte count is "<<bytecount<<endl;
  //Assign ArrayInputStream with enough memory 
  google::protobuf::io::ArrayInputStream ais(buffer,siz+4);
  CodedInputStream coded_input(&ais);
  //Read an unsigned integer with Varint encoding, truncating to 32 bits.
  coded_input.ReadVarint32(&siz);
  //After the message's length is read, PushLimit() is used to prevent the CodedInputStream 
  //from reading beyond that length.Limits are used when parsing length-delimited 
  //embedded messages
  google::protobuf::io::CodedInputStream::Limit msgLimit = coded_input.PushLimit(siz);
  //De-Serialize
  payload.ParseFromCodedStream(&coded_input);
  //Once the embedded message has been parsed, PopLimit() is called to undo the limit
  coded_input.PopLimit(msgLimit);
  //Print the message
  cout<<"Message is "<<payload.DebugString();

}

void* SocketHandler(void* lp){
    int *csock = (int*)lp;

        char buffer[4];
        int bytecount=0;
        string output,pl;
        log_packet logp;

        memset(buffer, '\0', 4);

        while (1) {
        //Peek into the socket and get the packet size
        if((bytecount = recv(*csock,
                         buffer,
                                 4, MSG_PEEK))== -1){
                fprintf(stderr, "Error receiving data %d\n", errno);
        }else if (bytecount == 0)
                break;
        cout<<"First read byte count is "<<bytecount<<endl;
        readBody(*csock,readHdr(buffer));
        }

FINISH:
        free(csock);
    return 0;
}

型

赞(0）分享  回复(0）举报  2023-08-03
9rnv2umw

9rnv2umw2#

不幸的是，protobuf并没有提供一种方法来“打包”（定界）你的消息：
如果要将多条消息写入单个文件或流，则由您来跟踪一条消息的结束位置和下一条消息的开始位置。协议缓冲区连线格式不是自定界的，因此协议缓冲区分析器无法自行确定消息的结束位置。解决此问题的最简单方法是在编写消息本身之前编写每个消息的大小。
(from documentation）
所以，他们基本上建议你达到相同的解决方案。

赞(0）分享  回复(0）举报  2023-08-03
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