使用C套接字在HTTP响应中发送二进制文件

Question

我试图在http响应中发送二进制文件(png图像).

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);
    }
}

但是我的浏览器不理解这个=(我到底做错了什么？

UPD:我试图发送文本数据 - 没关系.但二进制数据失败了

Answer 1

问题是,你的邮件正文被视为空值终止字符串(您使用strcat,并strlen在其上),当它是不是一个:它是二进制数据(PNG文件).因此,strcat与strlen两个停止对图像(通常非常早)在所述第一字节0.

你的程序甚至打印出响应体:注意它给出了正确的头,但是一旦PNG头(二进制数据)启动,只有几个字节.

1. 该行strcat(reply, buffer),buffer可能包含0个字节.将其更改为memcpy(reply+strlen(header), buffer, fileLen).
2. 该行send(client, reply, strlen(reply), 0),reply可能包含0个字节.预先计算回复的长度,或用strlen(header)+fileLen.替换strlen .

另一个错误是,当你完成后你没有关闭连接,所以浏览器将永远等待.你需要这个,之后send:

close(client);