下载跟这个没关系的。

贴一段 Perl 的 CGI::Application::Plugin::Stream，这是用于在服务器端
发送文件的，可以看到 -type 用的是真实的 mime type，不是一律 octet-stream。

http://cpansearch.perl.org/src/PURDY/CGI-Application-Plugin-Stream-2.10/lib/CGI/Application/Plugin/Stream.pm

    # Use FileHandle to make File::MMagic happy;
    # bless the filehandle into the FileHandle package to make File::MMagic happy
    require FileHandle;
    bless $fh,  "FileHandle";

    # Check what headers the user has already set and
    # don't override them.
    my %existing_headers = $self->header_props();

    # Check for a existing type header set with or without a hypheout a hyphen
    unless ( $existing_headers{'-type'} ||  $existing_headers{'type'} ) {
        my $mime_type;

        eval {
            require File::MMagic;
            my $magic = File::MMagic->new();
            $mime_type = $magic->checktype_filehandle($fh);
        };
        warn "Failed to load File::MMagic module to determine mime type: $@" if $@;
        
        # Set Default
        $mime_type ||= 'application/octet-stream';

        $self->header_add('-type' => $mime_type);
    }


    unless ( $existing_headers{'Content_Length'}
        ||   $existing_headers{'-Content_Length'}
        ) {
        $self->header_add('-Content_Length' => $size);
    }

    unless ( $existing_headers{'-attachment'}
        ||   $existing_headers{'attachment'}
        ||   grep( /-?content-disposition/i, keys %existing_headers )
        ) {
        $self->header_add('-attachment' => $basename);
    }

【 在 elf (精灵 | bbs.rains.cn 小雨如丝BBS) 的大作中提到: 】
: 还有一个header
: Content-Type: application/octet-stream
--
FROM 211.157.41.*