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我有两个程序，recvfile.py 和 sendfile.cpp。它们可以工作，只是我在新文件的末尾有一堆额外的换行符。我不知道额外的空间是如何到达那里的。我知道问题出在发件人方面，因为当我使用 python 的 sendall() 函数发送文件时不会发生同样的情况。

以下是文件：

jmm_sockets.c

#include <winsock.h>
#include <stdio.h>
#include <stdlib.h>

int getServerSocket(int port)
{
  WSADATA wsaData;
  if(WSAStartup(MAKEWORD(2,0), &wsaData) != 0){
    fprintf(stderr, "WSAStartup() failed\n");
    exit(1);
  }

  // create socket for incoming connections
  int servSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if(servSock == INVALID_SOCKET){
    fprintf(stderr, "Oops: socket() failed %d\n", WSAGetLastError());
    exit(1);
  }

  // construct local address structure
  struct sockaddr_in servAddr;
  memset(&servAddr, 0, sizeof(servAddr));
  servAddr.sin_family = AF_INET;
  servAddr.sin_addr.s_addr = INADDR_ANY;
  servAddr.sin_port = htons(port);

  // bind to the local address
  int servAddrLen = sizeof(servAddr);
  if(bind(servSock, (SOCKADDR*)&servAddr, servAddrLen) == SOCKET_ERROR){
    fprintf(stderr, "Oops: bind() failed %d\n", WSAGetLastError());
    exit(1);
  }

  return servSock;
}

int getClientSocket(char* host, int port)
{
  WSADATA wsaData;
  if(WSAStartup(MAKEWORD(2,0), &wsaData) != 0){
    fprintf(stderr, "Oops: WSAStartup() failed");
    exit(1);
  }

  // create tcp socket
  int sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if(socket<0){
    fprintf(stderr, "Oops: socket() failed %d\n", WSAGetLastError());
    exit(1);
  }

  // set up serverAddr structure
  struct sockaddr_in servAddr;
  memset(&servAddr, 0, sizeof(servAddr));
  servAddr.sin_family = AF_INET;
  servAddr.sin_addr.s_addr = inet_addr(host);
  servAddr.sin_port = htons(port);

  // connecet to server address
  if(connect(sock, (SOCKADDR*)&servAddr, sizeof(servAddr)) < 0){
    fprintf(stderr, "Oops: connect() failed. %d\n", WSAGetLastError());
    exit(1);
  }

  return sock;
}

发送文件.cpp：

#include "jmm_sockets.h"
#include <windows.h>
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <sys/stat.h>
using namespace std;

int main(int argc, char** argv)
{
  int port;
  string host;
  string filename;

  if(argc==2){
    cout << "Host: ";
    cin >> host;

    cout << "Port: ";
    cin >> port;

    filename = argv[1];
  }else if (argc == 4){
    host = argv[1];
    port = atoi(argv[2]);
    filename = argv[3];
  }else{
    cerr << "Usage: " << argv[0] << " [<host> <port>] <filename>" << endl;
    exit(1);
  }

  // open file for reading
  ifstream fin;
  fin.open(filename.c_str());
  if(fin.fail()){
    cerr << "Error: opening " << filename << " failed. " << endl;
    exit(1);
  }

  // get file size
  fin.seekg(0, ios::end);
  int size = fin.tellg();
  fin.seekg(0, ios::beg);

  // open socket for sending
  int sock = getClientSocket((char*)host.c_str(), port);

  // send file size
  char buffer[16];
  itoa(size, buffer, 10);
  int i;
  for(i=0; i<strlen(buffer); i++){
    if(send(sock, &buffer[i], 1, 0)!=1){
      cerr << "Error: send() failed " << WSAGetLastError() << endl;
      exit(1);
    }
  }
  char c = '\n';
  if(send(sock, &c, 1, 0)!=1){
    fprintf(stderr, "Error: send() failed %d\n", WSAGetLastError());
    exit(1);
  }

  // recv y or n
  int recvMsgSize = recv(sock, &c, 1, 0);
  if(recvMsgSize!=1){
    fprintf(stderr, "Error: recv() failed %d\n", WSAGetLastError());
    exit(1);
  }

  if(c=='y'){
    // send entire file
    int readSoFar = 0;
    while(readSoFar < size){
      fin.get(c);
      if(send(sock, &c, 1, 0)!=1){
    cerr << "Error: send() failed " << WSAGetLastError() << endl;
    exit(1);
      }
      readSoFar++;
    }

  }else if (c=='n'){
    // leave
    cout << "Remote host declined file." << endl;
  }

  fin.close();
  closesocket(sock);
  WSACleanup();

  // 
  return 0;
}

最后，recvfile.py：

import sys
from jmm_sockets import *
import yesno

if len(sys.argv) != 2:
    print "Usage: ", argv[0], "<port>"

s = getServerSocket(None, int(sys.argv[1]))
conn, addr = s.accept()

buffer = None
filelen = str()

# receive filesize
while 1:
    buffer = conn.recv(1)
    if buffer == '\n':
        # give it a rest
        break
    else:
        filelen = filelen + buffer

# prompt user to accept file
filelen = int(filelen)
print "file size = ", filelen,
userChoice = yesno.yesno("Accept?")
conn.send(userChoice)

# conditionally accecpt file
if bool(userChoice):
    filename = raw_input("What do you want to call the file? ")
    f = open(filename, 'w')

    buffer = None
    data = str()
    recvdBytes = 0
    while recvdBytes < filelen:
        buffer = conn.recv(1)
        recvdBytes = recvdBytes + 1
        data = data + buffer

print "File: ",
f.write(data)
print "written"
conn.close()
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1 回答 1

2

您最终使用额外换行符的原因是因为您通过套接字发送了额外的换行符，这是因为您尝试发送的数据超出了您的预期。

如果您检查了fail()输入文件的状态fin，您会发现它在最后几次调用时都失败了fin.get(c)，因此 的值c保持不变——它保持为换行符，这是输入文件中的最后一个字符。

这是由于CRLF 转换而发生的：您使用的文件大小（size变量）是磁盘上的原始文件大小，计算所有 CR。但是，当您以文本模式打开它并一次读取一个字节时，标准库会默默地将所有 CRLF 转换为 LF，因此您不会通过套接字发送 CR。因此，您在此过程结束时获得的额外换行数等于原始文件中的换行数。

解决此问题的方法是以二进制模式打开文件以禁用 CRLF 转换：

fin.open(filename.c_str(), ios::in | ios::binary);

此外，您不应该一次发送一个字节的文件——这非常慢。如果你不走运，你将为每个字节发送一个完整的数据包。如果幸运的话，您的操作系统的网络堆栈会将这些多次发送累积成更大的数据包（不要依赖于此），但即便如此，您仍然会对内核进行大量系统调用。

考虑重构代码以减少对send()andrecv()的调用，每次调用传递大量字节，例如：

// Just use one call to send instead of looping over bytes and sending one
// byte at a time.  Simpler and faster!
send(sock, buffer, strlen(buffer), 0);
于 2010-05-25T18:45:33.507 回答