Let's start with simple prints...

glendasayfs.c

@@ -0,0 +1,85 @@
+/* Very rudimentary 9P fileserver */
+
+#include <u.h>
+#include <libc.h>
+#include <mp.h>
+#include <fcall.h>
+#include <thread.h>
+#include <9p.h>
+
+Tree *glendatree;
+typedef enum {QCTL} qpath;
+
+Srv fs = {
+    //.open = fsopen,
+    .read = fsread,
+    .write= fswrite
+};
+
+/*
+ * 0222 /ctl
+ *      say <n>
+ */
+
+char*
+ctlparse(char *line,  int len)
+{
+    /* line is not null terminated */
+    if(strncmp(line, "say", 3) == 0){
+
+ 	fprint(1,"(\\(\\ \n");
+ 	fprint(1,"( . .)\n");
+ 	fprint(1," | ° ¡\n");
+ 	fprint(1," ¿   ;\n");
+ 	fprint(1,"c?.UJ\n");
+    } 
+    /* could potentially add more commands in a switch */
+    return nil;
+}
+
+
+void
+fswrite(Req *r) {
+    switch(r->fid->qid.path) {
+        case QCTL:
+            ctlparse(r->ifcall.data, r->ifcall.count);
+            break;
+        default:
+            break;
+    }
+    respond(r, nil);
+}
+
+void
+fsread(Req *r) {
+    return nil;
+}
+
+void usage(void)
+{
+    fprint(2,"usage: glendasayfs [-D] [-m mntpt]\n");
+    exits("usage");
+}
+
+void
+main(int argc,char *argv[])
+{
+    char *mntpt = "/n/glendasay";
+
+    ARGBEGIN{
+        case 'D':
+            chatty9p++;
+            break;
+        case 'm':
+            mntpt = EARGF(usage());
+            break;
+
+    }ARGEND;
+
+    /* Create file tree and populate */
+    fs.tree = glendatree = alloctree("none","none",DMDIR|0555,nil);
+    closefile(createfile(glendatree->root,"ctl","none",0222,nil)); // write only
+    postmountsrv(&fs,nil,mntpt,MAFTER);
+
+    exits(nil);
+}