使用C套接字发送二进制文件中的HTTP响应 [英] Send binary file in HTTP response using C sockets

问题描述

我真的试图在http响应发送一个二进制文件（png图片）。

I`m trying to send a binary file (png image) in http response.

FILE *file;
char *buffer;
int fileLen;

//Open file
file = fopen("1.png", "rb");
if (!file)
{
    return;
}

//Get file length
fseek(file, 0, SEEK_END);
fileLen=ftell(file);
fseek(file, 0, SEEK_SET);

//Allocate memory
buffer=(char *)malloc(fileLen+1);
if (!buffer)
{
    fprintf(stderr, "Memory error!");
    fclose(file);
    return;
}

//Read file contents into buffer
fread(buffer, fileLen, 1, file);
fclose(file);
//free(buffer);




char header[102400];

sprintf(header, 
"HTTP/1.1 200 OK\n"
"Date: Thu, 19 Feb 2009 12:27:04 GMT\n"
"Server: Apache/2.2.3\n"
"Last-Modified: Wed, 18 Jun 2003 16:05:58 GMT\n"
"ETag: \"56d-9989200-1132c580\"\n"
"Content-Type: image/png\n"
"Content-Length: %i\n"
"Accept-Ranges: bytes\n"
"Connection: close\n"
        "\n", fileLen);

char *reply = (char*)malloc(strlen(header)+fileLen);
strcpy(reply, header);
strcat(reply, buffer);

printf("msg %s\n", reply);


//return 0;
int sd = socket(PF_INET, SOCK_STREAM, 0);

struct sockaddr_in addr;
bzero(&addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(8081);
addr.sin_addr.s_addr = INADDR_ANY;

if(bind(sd,&addr,sizeof(addr))!=0)
{
    printf("bind error\n");
}

if (listen(sd, 16)!=0)
{
    printf("listen error\n");
}

for(;;)
{
    int size = sizeof(addr);
    int client = accept(sd, &addr, &size);

    if (client > 0)
    {
        printf("client connected\n");
        send(client, reply, strlen(reply), 0);
    }
}

但我的浏览器不明白这个=（什么我做错了什么呢？

but my browser does not understand this =( What am I doing wrong exactly?

UPD：我试图发送文本数据 - 它的确定。但是，二进制数据失败

UPD: I tried to send text data - its OK. But binary data fails

推荐答案

的问题是，你的邮件正文被视为空值终止的文本字符串（使用 strcat的和的strlen 就可以了），当它不是一：它是二进制数据（PNG文件）。因此， strcat的和的strlen 都停在图像（通常是比较早）在第0字节。

The problem is that your message body is being treated as a null-terminated text string (you use strcat and strlen on it), when it isn't one: it is binary data (a PNG file). Therefore, strcat and strlen both stop on the first 0 byte in the image (typically quite early).

您的程序，即使打印出响应体：注意到它提供正确的标题，但一旦PNG头（二进制数据）开始，只有几个字节

Your program is even printing out the response body: notice that it gives the correct header, but that once the PNG header (binary data) starts, there is only a few bytes.

1. 行 strcat的（回复，缓冲），其中缓存可能包含0字节。将其更改为的memcpy（回复+ strlen的（头），缓冲，fileLen）。


2. 行发送（客户端，回复，strlen的（回复），0），其中回复可能包含0字节。 pre-计算答复的长短，或更换的strlen与的strlen（头）+ fileLen 。

1. The line strcat(reply, buffer), where buffer potentially contains 0 bytes. Change it to memcpy(reply+strlen(header), buffer, fileLen).
2. The line send(client, reply, strlen(reply), 0), where reply potentially contains 0 bytes. Pre-calculate the length of the reply, or replace the strlen with strlen(header)+fileLen.

另外一个错误是，你是不是关闭连接当你完成，所以浏览器只是等待。你需要这个，以后发送：

Another bug is that you aren't closing the connection when you're done, so the browser will just wait forever. You need this, after send:

close(client);

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