HTTP request and response headers examples using telnet

yu$ telnet www.google.com 80
Trying 64.233.189.99...
Connected to www.l.google.com.
Escape character is '^]'.
GET /intl/en_ALL/images/logo.gif HTTP/1.1
Host: www.google.com
User-Agent: Mozilla/5.0(Robots) Gecko/20061206 Firefox/1.5.0.9
Accept-Encoding: gzip,deflate

HTTP/1.1 200 OK
Content-Type: image/gif
Last-Modified: Wed, 07 Jun 2006 19:38:24 GMT
Expires: Sun, 17 Jan 2038 19:14:07 GMT
Server: gws
Content-Length: 8558
Age: 13
Date: Sun, 06 Apr 2008 06:51:56 GMT

GIF89an.....

yu$ telnet www.google.com 80
Trying 64.233.189.104...
Connected to www.l.google.com.
Escape character is '^]'.
GET /intl/en_ALL/images/logo.gif HTTP/1.1
Host: www.google.com
User-Agent: Mozilla/5.0(Robots) Gecko/20061206 Firefox/1.5.0.9
Accept-Encoding: gzip,deflate
If-Modified-Since: Wed, 07 Jun 2006 19:38:24 GMT

HTTP/1.1 304 Not Modified
Date: Sun, 06 Apr 2008 06:53:10 GMT
Server: GFE/1.3

yu$ telnet l.yimg.com 80
Trying 203.209.246.249...
Connected to geoycs-l.yahoo8.akadns.net.
Escape character is '^]'.
GET /a/i/ww/news/2008/04/04/crocodile-sm.jpg HTTP/1.1
Host: l.yimg.com
User-Agent: Mozilla/5.0(Robots) Gecko/20061206 Firefox/1.5.0.9
Accept-Encoding: gzip,deflate
Connection: keep-alive

HTTP/1.1 200 OK
Date: Sat, 05 Apr 2008 00:14:27 GMT
Cache-Control: max-age=315360000
Expires: Tue, 03 Apr 2018 00:14:27 GMT
Last-Modified: Fri, 04 Apr 2008 17:49:26 GMT
Accept-Ranges: bytes
Content-Length: 860
Content-Type: image/jpeg
Age: 133250
Connection: keep-alive
Server: YTS/1.16.0



Connection closed by foreign host.

In HTTP/1.1 the ETag and If-None-Match headers are another way to make conditional GET requests.

<IMG ALT="Red Star"
SRC="data:image/gif;base64,R0lGODlhDAAMALMLAPN8ffBiYvWW
lvrKy/FvcPewsO9VVfajo+w6O/zl5estLv/8/AAAAAAAAAAAAAAAACH5BAEA
AAsALAAAAAAMAAwAAAQzcElZyryTEHyTUgknHd9xGV+qKsYirKkwDYiKDBia
tt2H1KBLQRFIJAIKywRgmhwAIlEEADs=">

Apache2 mod_headers using to modify http response headers

将mod_headers.so复制到modules目录下，修改httpd.conf文件：

LoadModule headers_module modules/mod_headers.so
Header add P3P "CP=\"CURa ADMa DEVa PSAo PSDo OUR BUS UNI PUR INT DEM STA PRE COM NAV OTC NOI DSP COR\""
Header set TEST "%D %t"

其中Header可添加在Context: server config, virtual host, directory, .htaccess
Reference: http://httpd.apache.org/docs/1.3/mod/mod_headers.html
http://httpd.apache.org/docs/2.2/mod/mod_headers.html

Rails controller request and response methods and instance_variables

class TestController < ApplicationController
  before_filter { |controller| p controller.request.methods.sort; p controller.request.instance_variables }
  after_filter { |controller| p controller.response.methods.sort; p controller.response.instance_variables }
  
  def index
  end
end

# ["==", "===", "=~", "__id__", "__send__", "`", "accepts", "b64encode", "blank?", "cgi", "cgi=", "class", "clone", "content_type", "cookies", "copy_instance_variables_from", "daemonize", "dclone", "decode64", "decode_b", "delete?", "display", "domain", "dup", "enable_warnings", "encode64", "env", "eql?", "equal?", "extend", "extend_with_included_modules_from", "extended_by", "formatted_post?", "freeze", "frozen?", "gem", "get?", "hash", "head?", "host", "host_with_port", "id", "inspect", "instance_eval", "instance_exec", "instance_of?", "instance_values", "instance_variable_get", "instance_variable_set", "instance_variables", "is_a?", "kind_of?", "load", "method", "method_missing", "methods", "nil?", "object_id", "parameters", "path", "path_parameters", "path_parameters=", "port", "port_string", "post?", "post_format", "pretty_inspect", "pretty_print", "pretty_print_cycle", "pretty_print_inspect", "pretty_print_instance_variables", "private_methods", "protected_methods", "protocol", "public_methods", "put?", "query_parameters", "query_string", "raw_post", "relative_url_root", "relative_url_root=", "remote_ip", "remove_subclasses_of", "request_parameters", "request_uri", "require", "require_gem", "require_library_or_gem", "reset_session", "respond_to?", "returning", "send", "server_software", "session", "session=", "session_options", "session_options=", "silence_stderr", "silence_stream", "silence_warnings", "singleton_methods", "ssl?", "standard_port", "subclasses_of", "subdomains", "suppress", "symbolized_path_parameters", "taguri", "taguri=", "taint", "tainted?", "to_a", "to_json", "to_param", "to_s", "to_yaml", "to_yaml_properties", "to_yaml_style", "type", "unloadable", "untaint", "with_options", "xhr?", "xml_http_request?", "xml_post?", "yaml_post?"]
# ["@session", "@request_method", "@query_parameters", "@parameters", "@content_type", "@request_parameters", "@session_options", "@session_options_with_string_keys", "@symbolized_path_parameters", "@env", "@cgi", "@path_parameters"]
# ["==", "===", "=~", "__id__", "__send__", "`", "assigns", "assigns=", "b64encode", "blank?", "body", "body=", "charset", "charset=", "class", "clone", "content_type", "content_type=", "cookies", "cookies=", "copy_instance_variables_from", "daemonize", "dclone", "decode64", "decode_b", "display", "dup", "enable_warnings", "encode64", "eql?", "equal?", "extend", "extend_with_included_modules_from", "extended_by", "freeze", "frozen?", "gem", "hash", "headers", "headers=", "id", "inspect", "instance_eval", "instance_exec", "instance_of?", "instance_values", "instance_variable_get", "instance_variable_set", "instance_variables", "is_a?", "kind_of?", "layout", "layout=", "load", "method", "methods", "nil?", "object_id", "out", "pretty_inspect", "pretty_print", "pretty_print_cycle", "pretty_print_inspect", "pretty_print_instance_variables", "private_methods", "protected_methods", "public_methods", "redirect", "redirected_to", "redirected_to=", "redirected_to_method_params", "redirected_to_method_params=", "remove_subclasses_of", "require", "require_gem", "require_library_or_gem", "respond_to?", "returning", "send", "session", "session=", "silence_stderr", "silence_stream", "silence_warnings", "singleton_methods", "subclasses_of", "suppress", "taguri", "taguri=", "taint", "tainted?", "template", "template=", "to_a", "to_json", "to_param", "to_s", "to_yaml", "to_yaml_properties", "to_yaml_style", "type", "unloadable", "untaint", "with_options"]
# ["@session", "@headers", "@assigns", "@body", "@redirected_to", "@cgi", "@template"]