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POWeird HTTP problem/mistake with Lisp
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copied!<p>I'm attempting to learn a little more about handling sockets and network connections in SBCL; so I wrote a simple wrapper for HTTP. Thus far, it merely makes a stream and performs a request to ultimately get the header data and page content of a website.</p> <p>Until now, it has worked at somewhat decently. Nothing to brag home about, but it at least worked.</p> <p>I have come across a strange problem, however; I keep getting "400 Bad Request" errors.</p> <p>At first, I was somewhat leery about how I was processing the HTTP requests (more or less passing a request string as a function argument), then I made a function that formats a query string with all the parts I need and returns it for use later... but I still get errors.</p> <p>What's even more odd is that the errors don't happen every time. If I try the script on a page like Google, I get a "200 Ok" return value... but at other times on other sites, I'll get "400 Bad Request".</p> <p>I'm certain its a problem with my code, but I'll be damned if I know exactly what is causing it.</p> <p>Here is the code that I am working with:</p> <pre><code>(use-package :sb-bsd-sockets) (defun read-buf-nonblock (buffer stream) (let ((eof (gensym))) (do ((i 0 (1+ i)) (c (read-char stream nil eof) (read-char-no-hang stream nil eof))) ((or (>= i (length buffer)) (not c) (eq c eof)) i) (setf (elt buffer i) c)))) (defun http-connect (host &optional (port 80)) "Create I/O stream to given host on a specified port" (let ((socket (make-instance 'inet-socket :type :stream :protocol :tcp))) (socket-connect socket (car (host-ent-addresses (get-host-by-name host))) port) (let ((stream (socket-make-stream socket :input t :output t :buffering :none))) stream))) (defun http-request (stream request &optional (buffer 1024)) "Perform HTTP request on a specified stream" (format stream "~a~%~%" request ) (let ((data (make-string buffer))) (setf data (subseq data 0 (read-buf-nonblock data stream))) (princ data) (> (length data) 0))) (defun request (host request) "formated HTTP request" (format nil "~a HTTP/1.0 Host: ~a" request host)) (defun get-page (host &optional (request "GET /")) "simple demo to get content of a page" (let ((stream (http-connect host))) (http-request stream (request host request))) </code></pre>

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