I was testing out a port for quicklisp on MKCL, today. The file is attached as revised from the original  at http://beta.quicklisp.org/quicklisp.lisp It was a straightforward patch, focusing mostly on sockets support. Basically I just copied the quicklisp implementation package definition for SBCL, with some minor revisions. I was testing it out, then, when I encountered the following error. I'm not sure if the error may be a matter of the patched quicklisp - going by the debugger output, I'd like to assume it may be a matter of socket streams. It looks like quicklisp implements its own HTTP client. Maybe there could be a workaround possible, somewhere in that client code? I wasn't certain about sending the patch to the quicklisp developers, given this 'feature'.  Looking at the debugger output, it looks like the error was in mkcl_safe_fclose failing on a socket-output-stream due to a bad FD. Here's the debugger output and backtrace. -- Sean during (quicklisp-quickstart:install) ; Fetching #<QLQS-HTTP::URL "http://beta.quicklisp.org/quickstart/asdf.lisp"> ; 159.59KB ================================================== 163,424 bytes in 0.77 seconds (206.56KB/sec) ; Fetching #<QLQS-HTTP::URL "http://beta.quicklisp.org/quickstart/quicklisp.tar"> ; 210.00KB ================================================== 215,040 bytes in 1.03 seconds (203.16KB/sec) ; Fetching #<QLQS-HTTP::URL "http://beta.quicklisp.org/quickstart/setup.lisp"> ; 4.88KB ================================================== 4,995 bytes in 0.00 seconds (5546.73KB/sec) Debugger called in: #<thread "Initial" (3737) 00000000010b7d80>. Filesystem error with pathname: #<output stream "SOCKET-OUTPUT-STREAM">. mkcl_safe_fclose() failed. OS Explanation: (errno == 9) Bad file descriptor. [...restarts...] Broken at IHS[73]> C::COMPILER-DEBUGGER. In: #<thread "Initial" (3560) 000000000164fd80>.  File: "/home/user/workspaces/workspace_gpcl/3rdparty/mkcl-1.0.1/src/cmp/cmputil.lsp" (Position #4195) QL-UTIL>> :b Backtrace:   IHS[117]> COMPILER-DEBUGGER   IHS[116]> lambda, closure generated from compile-file   IHS[114]> handle-internal-error   IHS[113]> signal   IHS[111]> wrapped-method-function   IHS[110]> standard-compute-effective-method   IHS[109]> compute-effective-method   IHS[108]> compute-effective-method, closure generated from nil   IHS[107]> compute-make-instance-function   IHS[106]> make-instance_nil_class   IHS[105]> lambda, closure generated from wrapped-method-function   IHS[104]> make-condition   IHS[101]> allocate-instance_nil_class   IHS[100]> lambda, closure generated from wrapped-method-function   IHS[99]> class-prototype_nil_class   IHS[98]> lambda, closure generated from wrapped-method-function   IHS[97]> compute-make-instance-function   IHS[96]> make-instance_nil_class   IHS[95]> lambda, closure generated from wrapped-method-function   IHS[94]> make-condition   IHS[91]> make-c1form*   IHS[90]> c1c-inline   IHS[89]> c1call-symbol   IHS[88]> c1expr   IHS[87]> c1stack-push-values   IHS[86]> c1call-symbol   IHS[85]> c1expr   IHS[84]> t1/c1expr   IHS[83]> c1progn   IHS[82]> c1decl-body   IHS[81]> c1let   IHS[80]> c1call-symbol   IHS[79]> c1expr   IHS[78]> c1with-stack   IHS[77]> c1call-symbol   IHS[76]> c1expr   IHS[75]> c1multiple-value-prog1   IHS[74]> c1call-symbol   IHS[73]> c1expr   IHS[72]> c1unwind-protect   IHS[71]> c1call-symbol   IHS[70]> c1expr   IHS[69]> t1/c1expr   IHS[68]> c1progn   IHS[67]> c1decl-body   IHS[66]> c1let   IHS[65]> c1call-symbol   IHS[64]> c1expr   IHS[63]> c1call-symbol   IHS[62]> c1expr   IHS[61]> t1/c1expr   IHS[60]> c1progn   IHS[59]> c1block   IHS[58]> c1call-symbol   IHS[57]> c1expr   IHS[56]> t1/c1expr   IHS[55]> c1progn   IHS[54]> c1decl-body   IHS[53]> c1locally   IHS[52]> c1call-symbol   IHS[51]> c1expr   IHS[50]> c1lambda-expr   IHS[49]> c1compile-function   IHS[48]> c1function   IHS[47]> c1call-symbol   IHS[46]> c1expr   IHS[45]> c1fset   IHS[44]> c1call-symbol   IHS[43]> c1expr   IHS[42]> t1ordinary   IHS[41]> t1expr*   IHS[40]> t1/c1expr   IHS[39]> c1progn   IHS[38]> c1eval-when   IHS[37]> t1expr*   IHS[36]> t1/c1expr   IHS[35]> c1progn   IHS[34]> t1expr*   IHS[33]> t1expr*   IHS[32]> t1expr   IHS[31]> lambda, closure generated from compile-file   IHS[30]> do-compilation-unit   IHS[29]> compile-file   IHS[28]> compile-file*   IHS[27]> perform_nil_compile-op_cl-source-file   IHS[26]> lambda, closure generated from wrapped-method-function   IHS[25]> lambda, closure generated from standard-main-effective-method   IHS[24]> perform-with-restarts_nil_t_t   IHS[23]> lambda, closure generated from wrapped-method-function   IHS[22]> perform-with-restarts_nil_compile-op_cl-source-file, closure generated from nil   IHS[21]> lambda, closure generated from wrapped-method-function   IHS[20]> lambda, closure generated from combine-method-functions   IHS[19]> lambda, closure generated from operate_nil_t_t   IHS[18]> do-compilation-unit   IHS[17]> do-compilation-unit   IHS[16]> operate_nil_t_t   IHS[15]> lambda, closure generated from wrapped-method-function   IHS[14]> lambda, closure generated from standard-main-effective-method   IHS[13]> oos   IHS[12]> bytecode [Evaluation of: (let ((*compile-print* nil) (*compile-verbose* nil) (*load-verbose* nil) (*load-print* nil)) (asdf:oos 'asdf:load-op "quicklisp" :verbose nil))]   IHS[11]> initial-install   IHS[10]> lambda   IHS[9]> lambda, closure generated from wrapped-method-function   IHS[8]> call-with-quiet-compilation   IHS[7]> install   IHS[6]> bytecode [Evaluation of: (quicklisp-quickstart:install)]   IHS[5]> lambda, closure generated from interactive-loop