HTTP 服务器未将完整文件发送到 WGET、Firefox。连接被对等方重置？

我正在编写一个 HTTP 服务器，但在发送较大的文件时遇到问题。如果我用 netcat 抓取它们，输出看起来很完美。如果我使用浏览器或 wget，有时我只能得到完整的文件。 WGET 不断收到“连接被对等方重置”错误，请参阅下面的输出。 Firefox 显示“连接已重置”。

下面是向客户端发送数据的相关流程：

int handle_request(int sockfd, struct cached_file content) {
    char buffer[1024]; // FIXME hardcoded arbitrary buffer size for header

    unsigned int sent_bytes;
    unsigned int total = 0;
    unsigned int bytes_left = content.size;

    printf("I have to send %u bytes of content.\n", content.size);

    snprintf(buffer, 1024, "HTTP/1.1 %s\nContent-Type: %s\nContent-Length: %s\n\n", content.statuscode, content.contenttype, content.sizestring);
    sent_bytes = send(sockfd, buffer, strlen(buffer), MSG_MORE);
    printf("I wanted to send %u bytes of header, and I sent %u.\n", strlen(buffer), sent_bytes);

    while (total < bytes_left) {
        sent_bytes = send(sockfd, content.data+total, bytes_left, 0);
        if (sent_bytes == -1) { 
            printf("send() returned -1\n");
            break; 
        }

        total      += sent_bytes;
        bytes_left -= sent_bytes;
    }
    printf("I sent %u bytes of content. I had %u left to send.\n", total, bytes_left);

    if (sent_bytes == -1)
        logprint("socket error!", errno);
}

这是 wget 尝试获取文件的输出：

wget --tries 1 http://localhost:8081/image.jpg
--2015-07-01 13:21:42--  http://localhost:8081/image.jpg
Resolving localhost (localhost)... ::1, 127.0.0.1
Connecting to localhost (localhost)|::1|:8081... failed: Connection refused.
Connecting to localhost (localhost)|127.0.0.1|:8081... connected.
HTTP request sent, awaiting response... 200 OK
Length: 700895 (684K) [image/jpeg]
Saving to: ‘image.jpg.10’

image.jpg.10                      53%[===============================>                             ] 363.31K  --.-KB/s   in 0.001s 

2015-07-01 13:21:42 (688 MB/s) - Read error at byte 372031/700895 (Connection reset by peer). Giving up.

wget --tries 1 http://localhost:8081/image.jpg
--2015-07-01 13:21:43--  http://localhost:8081/image.jpg
Resolving localhost (localhost)... ::1, 127.0.0.1
Connecting to localhost (localhost)|::1|:8081... failed: Connection refused.
Connecting to localhost (localhost)|127.0.0.1|:8081... connected.
HTTP request sent, awaiting response... 200 OK
Length: 700895 (684K) [image/jpeg]
Saving to: ‘image.jpg.11’

image.jpg.11                       6%[==>                                                          ]  42.69K  --.-KB/s   in 0s     

2015-07-01 13:21:43 (500 MB/s) - Read error at byte 43711/700895 (Connection reset by peer). Giving up.

调试 http 服务器的输出：

I have to send 700895 bytes of content.
I wanted to send 65 bytes of header, and I sent 65.
I sent 700895 bytes of content. I had 0 left to send.

我希望能有另一双眼睛来关注此事！为什么会发生这种情况以及如何解决它？

我的猜测是该错误与您未在此处显示的代码有关。

简单实现中的一个常见错误是没有完全读取请求，而是只读取第一行或一些字节来确定请求的页面，然后发送响应并最后关闭。

由于在关闭时仍有来自客户端的未读数据，这将导致对等方重置连接。使用 nc 时看不到这种效果，因为使用 nc 发送的请求可能比浏览器发出的请求短，因此在 nc 情况下会读取请求中的所有数据，但在浏览器情况下不会读取。

除此之外，即使浏览器接受您的响应也是无效的。您的状态行（第一行）在状态代码之后停止，而不是添加原因短语，请参阅http://www.w3.org/Protocols/rfc2616/rfc2616-sec6.html#sec6.1 http://www.w3.org/Protocols/rfc2616/rfc2616-sec6.html#sec6.1。另外，你使用\n代替\r\n作为行分隔符。