c++ - 通过套接字发送文件太慢

Question

我是新来的（我的第一个问题），而且有点新手，我从来没有上过编程课，所以......对于一些混乱的代码感到抱歉。

我制作了这个程序，通过套接字发送（客户端）和接收（服务器）文件，客户端每个循环读取和发送 1024 个字节的文件，服务器接收它并将其写入文件。它工作正常，但问题是它非常慢。将文件从我的计算机发送到我的计算机所需的时间与发送到另一台计算机所需的时间一样多，但仍然比预期的要多，当我尝试传输时，例如通过 Skype，它要快得多。有什么线索吗？（下面是我正在使用的代码）。

服务器：

// servrecvfile.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>

// Need to link with Ws2_32.lib
#pragma comment (lib, "Ws2_32.lib")
// #pragma comment (lib, "Mswsock.lib")

#define DEFAULT_BUFLEN 65536
#define DEFAULT_PORT "8883"

typedef struct thread_args{
    SOCKET ClientSocket;
    int index;
} *MYDATA, PM;

MYDATA pDataArray[100];
DWORD WINAPI abc(void*);

int p=0;

int abz(){
    return p;
}

void broadcast(MYDATA *fp, char *b, int index){
    for(int i=0; i<=abz(); i++){
        if(index != i)
            send( fp[i]->ClientSocket, b, (int)strlen(b), 0 );
    }
}

DWORD WINAPI abc(void* pVoid)
{   
    struct thread_args *fp;
    fp = (struct thread_args *) pVoid;
    long iResult;
    int filesize;
    unsigned char recvbuf[ DEFAULT_BUFLEN];
    memset(recvbuf, 0, sizeof(recvbuf));
    recv(fp->ClientSocket, (char*)recvbuf,  DEFAULT_BUFLEN, 0);
    FILE *abc = fopen(strtok ((char*)recvbuf,":"), "wb");
    filesize = atoi(strtok (NULL,":"));
    memset(recvbuf, 0, sizeof(recvbuf));
    int perc=0;
    int perc2=0;
    int counter=0;
    char a = '%';
        do {
            iResult = recv(fp->ClientSocket, (char*)recvbuf,  DEFAULT_BUFLEN, 0);
            if (iResult > 0) {
                counter += fwrite (recvbuf , sizeof(char) , iResult , abc );
                memset(recvbuf, 0, sizeof(recvbuf));
                perc2 = ((counter*1.000)/filesize*1.000)*100;
                if(perc2 != perc){
                    printf("%d%c\n", perc2, a);
                    perc = perc2;
                } 
            }
            else if (iResult == 0)
              printf("Connection closing...\n");
            else  {
              printf("recv failed with error: %d\n", WSAGetLastError());
              closesocket(fp->ClientSocket);
              fclose(abc);
              WSACleanup();
              ExitThread(1);
            }
        } while (iResult > 0);


        fclose(abc);
       ExitThread(-1);
}

int __cdecl main(void) 
{
    WSADATA wsaData;
    int iResult;

    SOCKET ListenSocket = INVALID_SOCKET;
    SOCKET ClientSocket = INVALID_SOCKET;

    struct addrinfo *result = NULL;
    struct addrinfo hints;

    int iSendResult;
    char recvbuf[DEFAULT_BUFLEN];
    int recvbuflen = DEFAULT_BUFLEN;


    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed with error: %d\n", iResult);
        return 1;
    }

    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

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

    // Create a SOCKET for connecting to server
    ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
    if (ListenSocket == INVALID_SOCKET) {
        printf("socket failed with error: %ld\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    // Setup the TCP listening socket
    iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    if (iResult == SOCKET_ERROR) {
        printf("bind failed with error: %d\n", WSAGetLastError());
        freeaddrinfo(result);
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    freeaddrinfo(result);

    iResult = listen(ListenSocket, SOMAXCONN);
    if (iResult == SOCKET_ERROR) {
        printf("listen failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    int i=0;
    while(1){

    // Accept a client socket
    ClientSocket = accept(ListenSocket, NULL, NULL);
    if (ClientSocket == INVALID_SOCKET) {
        printf("accept failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    pDataArray[i] = (MYDATA) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY,
                sizeof(PM));
    pDataArray[i]->ClientSocket = ClientSocket;
    pDataArray[i]->index = i;

        CreateThread( 
            NULL,                   // default security attributes
            0,                      // use default stack size  
            abc,       // thread function name
            pDataArray[i],          // argument to thread function 
            0,                      // use default creation flags 
            NULL);   // returns the thread identifier 
        p = i;
        i++;
    }

    // No longer need server socket
    closesocket(ListenSocket);

    // Receive until the peer shuts down the connection
    //char a[DEFAULT_BUFLEN];





    // shutdown the connection since we're done
    iResult = shutdown(ClientSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed with error: %d\n", WSAGetLastError());
        closesocket(ClientSocket);
        WSACleanup();
        return 1;
    }

    // cleanup
    closesocket(ClientSocket);
    WSACleanup();

    return 0;
}

客户：

// sendfile.cpp : Defines the entry point for the console application.
//
#include "StdAfx.h"

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>


// Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")


#define DEFAULT_BUFLEN 65536
#define DEFAULT_PORT "8882"


int __cdecl main(int argc, char **argv) 
{
    WSADATA wsaData;
    SOCKET ConnectSocket = INVALID_SOCKET;
    struct addrinfo *result = NULL,
                    *ptr = NULL,
                    hints;
    char *sendbuf = "this is a test";
    char recvbuf[DEFAULT_BUFLEN];
    int iResult;
    int recvbuflen = DEFAULT_BUFLEN;

    char linha[DEFAULT_BUFLEN];
    char IP[20], porta[10];

    FILE *fp1;
    fp1 = fopen("config.txt", "r");
    if(fp1 == NULL)
    {
        printf("Unable to find config.txt.\n");
        exit(-1);
    }
    while( fgets(linha,DEFAULT_BUFLEN,  fp1) !=NULL){
        if(strstr(linha, "port="))
            sscanf(linha, "port=%s", porta);
        if(strstr(linha, "ip="))
            sscanf(linha, "ip=%s", IP);
    }

    fclose(fp1);


    char filenam[DEFAULT_BUFLEN];
    printf("Insert file name: ");
    scanf ("%s", filenam);
    FILE *trans = fopen(filenam, "rb");

    if(trans == NULL)
    {
        printf("File not found\n");
        exit(-1);
    }


    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed with error: %d\n", iResult);
        return 1;
    }

    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(IP, porta, &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);
        if (ConnectSocket == INVALID_SOCKET) {
            printf("socket failed with error: %ld\n", WSAGetLastError());
            WSACleanup();
            return 1;
        }

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

    freeaddrinfo(result);

    if (ConnectSocket == INVALID_SOCKET) {
        printf("Unable to connect to server!\n");
        WSACleanup();
        return 1;
    }



    long lSize;

      // obtain file size:
    fseek (trans , 0 , SEEK_END);
    lSize = ftell (trans);
    rewind (trans);
    char a = '%';
  // allocate memory to contain the whole file:
    memset(recvbuf, 0, sizeof(recvbuf));
    unsigned char *linha2 = (unsigned char*) malloc (sizeof(unsigned char)* DEFAULT_BUFLEN);
    //send(ConnectSocket, filenam, (int)strlen(filenam), 0 );
    sprintf(filenam, "%s:%d", filenam, lSize);
    printf("%d %d\n", send(ConnectSocket, filenam, (int)strlen(filenam), 0 ), lSize);
    long counter=0;
    long read;
    int perc=0;
    int perc2=0;
    while(counter < lSize){
        read = fread_s(linha2,  DEFAULT_BUFLEN, sizeof(char),  DEFAULT_BUFLEN, trans);
        counter += send(ConnectSocket, (char*)linha2, read, 0);
        perc2 = ((counter*1.000)/lSize*1.000)*100;
        if(perc2 != perc){

            printf("%d%c\n", perc2, a);
            perc = perc2;
        } 

    }






    fclose(trans);
    /*
    do {
        //memset(a, 0, sizeof(a));
        iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
        if ( iResult > 0 )
        {
            printf("%s", recvbuf);
            memset(recvbuf, 0, sizeof(recvbuf));
        }
        else if ( iResult == 0 )
            printf("Connection closed\n");
        else
            printf("recv failed with error: %d\n", WSAGetLastError());


    } while( iResult > 0 ); */

    // cleanup
    closesocket(ConnectSocket);
    WSACleanup();

    return 0;
}

我在 Windows 7 上使用 Visual Studio 2010。

感谢任何帮助，如果这个问题的结构有什么问题，请告诉我。

Answer 1

Skype 可能会压缩文件，这将显着加快网络传输速度。您可以使用 zlib 内联压缩或从许多公开可用的（霍夫曼编码等）中实现自己的压缩。

顺便说一句，更改缓冲区大小不会对性能产生太大影响。底层 API（文件、套接字）已经过优化，可以自动处理缓冲，而与您读取/写入它们的方式无关。

Answer 2

为了通过套接字有效地发送文件数据，Windows 提供了TransmitFile函数。

Answer 3

首先运行 Wireshark 并跟踪网络通信。我预计您会受到默认 TCP 窗口大小的影响，从而导致不必要的流量控制。

看看这些答案可能会有所帮助：

• 有哪些好的 Wireshark 教程？
• 什么是 SO_SNDBUF 和 SO_RECVBUF
• 设置 recv 缓冲区大小如何影响 TCP Windows 大小。
• 为什么我对 TransmitFile 的调用与其他方法相比表现不佳？