diff --git a/concurrency-webserver/src/Makefile b/concurrency-webserver/src/Makefile
new file mode 100644
index 0000000..05444a9
--- /dev/null
+++ b/concurrency-webserver/src/Makefile
@@ -0,0 +1,26 @@
+# An admittedly primitive Makefile
+# To compile, type "make" or make "all"
+# To remove files, type "make clean"
+
+CC = gcc
+CFLAGS = -Wall
+OBJS = wserver.o wclient.o request.o io_helper.o 
+
+.SUFFIXES: .c .o 
+
+all: wserver wclient spin.cgi
+
+wserver: wserver.o request.o io_helper.o
+	$(CC) $(CFLAGS) -o wserver wserver.o request.o io_helper.o 
+
+wclient: wclient.o io_helper.o
+	$(CC) $(CFLAGS) -o wclient wclient.o io_helper.o
+
+spin.cgi: spin.c
+	$(CC) $(CFLAGS) -o spin.cgi spin.c
+
+.c.o:
+	$(CC) $(CFLAGS) -o $@ -c $<
+
+clean:
+	-rm -f $(OBJS) wserver wclient spin.cgi
diff --git a/concurrency-webserver/src/io_helper.c b/concurrency-webserver/src/io_helper.c
new file mode 100644
index 0000000..623caee
--- /dev/null
+++ b/concurrency-webserver/src/io_helper.c
@@ -0,0 +1,83 @@
+#include "io_helper.h"
+
+ssize_t readline(int fd, void *buf, size_t maxlen) {
+    char c;
+    char *bufp = buf;
+    int n;
+    for (n = 0; n < maxlen - 1; n++) { // leave room at end for '\0'
+	int rc;
+        if ((rc = read_or_die(fd, &c, 1)) == 1) {
+            *bufp++ = c;
+            if (c == '\n')
+                break;
+        } else if (rc == 0) {
+            if (n == 1)
+                return 0; /* EOF, no data read */
+            else
+                break;    /* EOF, some data was read */
+        } else
+            return -1;    /* error */
+    }
+    *bufp = '\0';
+    return n;
+}
+
+
+int open_client_fd(char *hostname, int port) {
+    int client_fd;
+    struct hostent *hp;
+    struct sockaddr_in server_addr;
+    
+    if ((client_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
+        return -1; 
+    
+    // Fill in the server's IP address and port 
+    if ((hp = gethostbyname(hostname)) == NULL)
+        return -2; // check h_errno for cause of error 
+    bzero((char *) &server_addr, sizeof(server_addr));
+    server_addr.sin_family = AF_INET;
+    bcopy((char *) hp->h_addr, 
+          (char *) &server_addr.sin_addr.s_addr, hp->h_length);
+    server_addr.sin_port = htons(port);
+    
+    // Establish a connection with the server 
+    if (connect(client_fd, (sockaddr_t *) &server_addr, sizeof(server_addr)) < 0)
+        return -1;
+    return client_fd;
+}
+
+int open_listen_fd(int port) {
+    // Create a socket descriptor 
+    int listen_fd;
+    if ((listen_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
+	fprintf(stderr, "socket() failed\n");
+	return -1;
+    }
+    
+    // Eliminates "Address already in use" error from bind
+    int optval = 1;
+    if (setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, (const void *) &optval, sizeof(int)) < 0) {
+	fprintf(stderr, "setsockopt() failed\n");
+	return -1;
+    }
+    
+    // Listen_fd will be an endpoint for all requests to port on any IP address for this host
+    struct sockaddr_in server_addr;
+    bzero((char *) &server_addr, sizeof(server_addr));
+    server_addr.sin_family = AF_INET; 
+    server_addr.sin_addr.s_addr = htonl(INADDR_ANY); 
+    server_addr.sin_port = htons((unsigned short) port); 
+    if (bind(listen_fd, (sockaddr_t *) &server_addr, sizeof(server_addr)) < 0) {
+	fprintf(stderr, "bind() failed\n");
+	return -1;
+    }
+    
+    // Make it a listening socket ready to accept connection requests 
+    if (listen(listen_fd, 1024) < 0) {
+	fprintf(stderr, "listen() failed\n");
+	return -1;
+    }
+    return listen_fd;
+}
+
+
diff --git a/concurrency-webserver/src/io_helper.h b/concurrency-webserver/src/io_helper.h
new file mode 100644
index 0000000..59275ca
--- /dev/null
+++ b/concurrency-webserver/src/io_helper.h
@@ -0,0 +1,95 @@
+#ifndef __IO_HELPER__
+#define __IO_HELPER__
+
+#include <arpa/inet.h>
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+typedef struct sockaddr sockaddr_t;
+
+// useful here: gcc statement expressions
+// http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
+// macro ({ ...; x; }) returns value 'x' for caller
+// e.g., macro 'fork_or_die()' below returns 'pid' value
+#define fork_or_die() \
+    ({ pid_t pid = fork(); assert(pid >= 0); pid; })
+#define execve_or_die(filename, argv, envp) \
+    assert(execve(filename, argv, envp) == 0); 
+#define wait_or_die(status) \
+    ({ pid_t pid = wait(status); assert(pid >= 0); pid; })
+#define gethostname_or_die(name, len) \
+    ({ int rc = gethostname(name, len); assert(rc == 0); rc; })
+#define setenv_or_die(name, value, overwrite) \
+    ({ int rc = setenv(name, value, overwrite); assert(rc == 0); rc; })
+#define chdir_or_die(path) \
+    assert(chdir(path) == 0); 
+#define open_or_die(pathname, flags, mode) \
+    ({ int rc = open(pathname, flags, mode); assert(rc >= 0); rc; })
+#define read_or_die(fd, buf, count) \
+    ({ ssize_t rc = read(fd, buf, count); assert(rc >= 0); rc; })
+#define write_or_die(fd, buf, count) \
+    ({ ssize_t rc = write(fd, buf, count); assert(rc >= 0); rc; })
+#define lseek_or_die(fd, offset, whence) \
+    ({ off_t rc = lseek(fd, offset, whence); assert(rc >= 0); rc; })
+#define close_or_die(fd) \
+    assert(close(fd) == 0); 
+#define select_or_die(n, readfds, writefds, exceptfds, timeout) \
+    ({ int rc = select(n, readfds, writefds, exceptfds, timeout); assert(rc >= 0); rc; })
+#define dup2_or_die(fd1, fd2) \
+    ({ int rc = dup2(fd1, fd2); assert(rc >= 0); rc; })
+#define stat_or_die(filename, buf) \
+    assert(stat(filename, buf) >= 0);
+#define fstat_or_die(fd, buf) \
+    { assert(fstat(fd, buf) >= 0); }
+#define mmap_or_die(addr, len, prot, flags, fd, offset) \
+    ({ void *ptr = mmap(addr, len, prot, flags, fd, offset); assert(ptr != (void *) -1); ptr; })
+#define munmap_or_die(start, length) \
+    assert(munmap(start, length) >= 0); 
+#define socket_or_die(domain, type, protocol) \
+    ({ int rc = socket(domain, type, protocol); assert(rc >= 0); rc; })
+#define setsockopt_or_die(s, level, optname, optval, optlen) \
+    { assert(setsockopt(s, level, optname, optval, optlen) >= 0); }
+#define bind_or_die(sockfd, my_addr, addrlen) \
+    { assert(bind(sockfd, my_addr, addrlen) >= 0); }
+#define listen_or_die(s, backlog) \
+    { assert(listen(s,  backlog) >= 0); }
+#define accept_or_die(s, addr, addrlen) \
+    ({ int rc = accept(s, addr, addrlen); assert(rc >= 0); rc; })
+#define connect_or_die(sockfd, serv_addr, addrlen) \
+    { assert(connect(sockfd, serv_addr, addrlen) >= 0); }
+#define gethostbyname_or_die(name) \
+    ({ struct hostent *p = gethostbyname(name); assert(p != NULL); p; })
+#define gethostbyaddr_or_die(addr, len, type) \
+    ({ struct hostent *p = gethostbyaddr(addr, len, type); assert(p != NULL); p; })
+
+// client/server helper functions 
+ssize_t readline(int fd, void *buf, size_t maxlen);
+int open_client_fd(char *hostname, int portno);
+int open_listen_fd(int portno);
+
+// wrappers for above
+#define readline_or_die(fd, buf, maxlen) \
+    ({ ssize_t rc = readline(fd, buf, maxlen); assert(rc >= 0); rc; })
+#define open_client_fd_or_die(hostname, port) \
+    ({ int rc = open_client_fd(hostname, port); assert(rc >= 0); rc; })
+#define open_listen_fd_or_die(port) \
+    ({ int rc = open_listen_fd(port); assert(rc >= 0); rc; })
+
+#endif // __IO_HELPER__
diff --git a/concurrency-webserver/src/request.c b/concurrency-webserver/src/request.c
new file mode 100644
index 0000000..b5b9ce4
--- /dev/null
+++ b/concurrency-webserver/src/request.c
@@ -0,0 +1,180 @@
+#include "io_helper.h"
+#include "request.h"
+
+//
+// Some of this code stolen from Bryant/O'Halloran
+// Hopefully this is not a problem ... :)
+//
+
+#define MAXBUF (8192)
+
+void request_error(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg) {
+    char buf[MAXBUF], body[MAXBUF];
+    
+    // Create the body of error message first (have to know its length for header)
+    sprintf(body, ""
+	    "<!doctype html>\r\n"
+	    "<head>\r\n"
+	    "  <title>OSTEP WebServer Error</title>\r\n"
+	    "</head>\r\n"
+	    "<body>\r\n"
+	    "  <h2>%s: %s</h2>\r\n" 
+	    "  <p>%s: %s</p>\r\n"
+	    "</body>\r\n"
+	    "</html>\r\n", errnum, shortmsg, longmsg, cause);
+    
+    // Write out the header information for this response
+    sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);
+    write_or_die(fd, buf, strlen(buf));
+    
+    sprintf(buf, "Content-Type: text/html\r\n");
+    write_or_die(fd, buf, strlen(buf));
+    
+    sprintf(buf, "Content-Length: %lu\r\n\r\n", strlen(body));
+    write_or_die(fd, buf, strlen(buf));
+    
+    // Write out the body last
+    write_or_die(fd, body, strlen(body));
+}
+
+//
+// Reads and discards everything up to an empty text line
+//
+void request_read_headers(int fd) {
+    char buf[MAXBUF];
+    
+    readline_or_die(fd, buf, MAXBUF);
+    while (strcmp(buf, "\r\n")) {
+	readline_or_die(fd, buf, MAXBUF);
+    }
+    return;
+}
+
+//
+// Return 1 if static, 0 if dynamic content
+// Calculates filename (and cgiargs, for dynamic) from uri
+//
+int request_parse_uri(char *uri, char *filename, char *cgiargs) {
+    char *ptr;
+    
+    if (!strstr(uri, "cgi")) { 
+	// static
+	strcpy(cgiargs, "");
+	sprintf(filename, ".%s", uri);
+	if (uri[strlen(uri)-1] == '/') {
+	    strcat(filename, "index.html");
+	}
+	return 1;
+    } else { 
+	// dynamic
+	ptr = index(uri, '?');
+	if (ptr) {
+	    strcpy(cgiargs, ptr+1);
+	    *ptr = '\0';
+	} else {
+	    strcpy(cgiargs, "");
+	}
+	sprintf(filename, ".%s", uri);
+	return 0;
+    }
+}
+
+//
+// Fills in the filetype given the filename
+//
+void request_get_filetype(char *filename, char *filetype) {
+    if (strstr(filename, ".html")) 
+	strcpy(filetype, "text/html");
+    else if (strstr(filename, ".gif")) 
+	strcpy(filetype, "image/gif");
+    else if (strstr(filename, ".jpg")) 
+	strcpy(filetype, "image/jpeg");
+    else 
+	strcpy(filetype, "text/plain");
+}
+
+void request_serve_dynamic(int fd, char *filename, char *cgiargs) {
+    char buf[MAXBUF], *argv[] = { NULL };
+    
+    // The server does only a little bit of the header.  
+    // The CGI script has to finish writing out the header.
+    sprintf(buf, ""
+	    "HTTP/1.0 200 OK\r\n"
+	    "Server: OSTEP WebServer\r\n");
+    
+    write_or_die(fd, buf, strlen(buf));
+    
+    if (fork_or_die() == 0) {                        // child
+	setenv_or_die("QUERY_STRING", cgiargs, 1);   // args to cgi go here
+	dup2_or_die(fd, STDOUT_FILENO);              // make cgi writes go to socket (not screen)
+	extern char **environ;                       // defined by libc 
+	execve_or_die(filename, argv, environ);
+    } else {
+	wait_or_die(NULL);
+    }
+}
+
+void request_serve_static(int fd, char *filename, int filesize) {
+    int srcfd;
+    char *srcp, filetype[MAXBUF], buf[MAXBUF];
+    
+    request_get_filetype(filename, filetype);
+    srcfd = open_or_die(filename, O_RDONLY, 0);
+    
+    // Rather than call read() to read the file into memory, 
+    // which would require that we allocate a buffer, we memory-map the file
+    srcp = mmap_or_die(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0);
+    close_or_die(srcfd);
+    
+    // put together response
+    sprintf(buf, ""
+	    "HTTP/1.0 200 OK\r\n"
+	    "Server: OSTEP WebServer\r\n"
+	    "Content-Length: %d\r\n"
+	    "Content-Type: %s\r\n\r\n", 
+	    filesize, filetype);
+    
+    write_or_die(fd, buf, strlen(buf));
+    
+    //  Writes out to the client socket the memory-mapped file 
+    write_or_die(fd, srcp, filesize);
+    munmap_or_die(srcp, filesize);
+}
+
+// handle a request
+void request_handle(int fd) {
+    int is_static;
+    struct stat sbuf;
+    char buf[MAXBUF], method[MAXBUF], uri[MAXBUF], version[MAXBUF];
+    char filename[MAXBUF], cgiargs[MAXBUF];
+    
+    readline_or_die(fd, buf, MAXBUF);
+    sscanf(buf, "%s %s %s", method, uri, version);
+    printf("method:%s uri:%s version:%s\n", method, uri, version);
+    
+    if (strcasecmp(method, "GET")) {
+	request_error(fd, method, "501", "Not Implemented", "server does not implement this method");
+	return;
+    }
+    request_read_headers(fd);
+    
+    is_static = request_parse_uri(uri, filename, cgiargs);
+    if (stat(filename, &sbuf) < 0) {
+	request_error(fd, filename, "404", "Not found", "server could not find this file");
+	return;
+    }
+    
+    if (is_static) {
+	if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) {
+	    request_error(fd, filename, "403", "Forbidden", "server could not read this file");
+	    return;
+	}
+	request_serve_static(fd, filename, sbuf.st_size);
+    } else {
+	if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode)) {
+	    request_error(fd, filename, "403", "Forbidden", "server could not run this CGI program");
+	    return;
+	}
+	request_serve_dynamic(fd, filename, cgiargs);
+    }
+}
diff --git a/concurrency-webserver/src/request.h b/concurrency-webserver/src/request.h
new file mode 100644
index 0000000..65d0422
--- /dev/null
+++ b/concurrency-webserver/src/request.h
@@ -0,0 +1,5 @@
+#ifndef __REQUEST_H__
+
+void request_handle(int fd);
+
+#endif // __REQUEST_H__
diff --git a/concurrency-webserver/src/spin.c b/concurrency-webserver/src/spin.c
new file mode 100644
index 0000000..7f04d6b
--- /dev/null
+++ b/concurrency-webserver/src/spin.c
@@ -0,0 +1,52 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#define MAXBUF (8192)
+
+//
+// This program is intended to help you test your web server.
+// You can use it to test that you are correctly having multiple threads
+// handling http requests.
+// 
+
+double get_seconds() {
+    struct timeval t;
+    int rc = gettimeofday(&t, NULL);
+    assert(rc == 0);
+    return (double) ((double)t.tv_sec + (double)t.tv_usec / 1e6);
+}
+
+
+int main(int argc, char *argv[]) {
+    // Extract arguments
+    double spin_for = 0.0;
+    char *buf;
+    if ((buf = getenv("QUERY_STRING")) != NULL) {
+	// just expecting a single number
+	spin_for = (double) atoi(buf);
+    }
+
+    double t1 = get_seconds();
+    while ((get_seconds() - t1) < spin_for)
+	sleep(1);
+    double t2 = get_seconds();
+    
+    /* Make the response body */
+    char content[MAXBUF];
+    sprintf(content, "<p>Welcome to the CGI program (%s)</p>\r\n", buf);
+    sprintf(content, "%s<p>My only purpose is to waste time on the server!</p>\r\n", content);
+    sprintf(content, "%s<p>I spun for %.2f seconds</p>\r\n", content, t2 - t1);
+    
+    /* Generate the HTTP response */
+    printf("Content-length: %lu\r\n", strlen(content));
+    printf("Content-type: text/html\r\n\r\n");
+    printf("%s", content);
+    fflush(stdout);
+    
+    exit(0);
+}
+
diff --git a/concurrency-webserver/src/wclient.c b/concurrency-webserver/src/wclient.c
new file mode 100644
index 0000000..ee39777
--- /dev/null
+++ b/concurrency-webserver/src/wclient.c
@@ -0,0 +1,92 @@
+//
+// client.c: A very, very primitive HTTP client.
+// 
+// To run, try: 
+//      client hostname portnumber filename
+//
+// Sends one HTTP request to the specified HTTP server.
+// Prints out the HTTP response.
+//
+// For testing your server, you will want to modify this client.  
+// For example:
+// You may want to make this multi-threaded so that you can 
+// send many requests simultaneously to the server.
+//
+// You may also want to be able to request different URIs; 
+// you may want to get more URIs from the command line 
+// or read the list from a file. 
+//
+// When we test your server, we will be using modifications to this client.
+//
+
+#include "io_helper.h"
+
+#define MAXBUF (8192)
+
+//
+// Send an HTTP request for the specified file 
+//
+void client_send(int fd, char *filename) {
+    char buf[MAXBUF];
+    char hostname[MAXBUF];
+    
+    gethostname_or_die(hostname, MAXBUF);
+    
+    /* Form and send the HTTP request */
+    sprintf(buf, "GET %s HTTP/1.1\n", filename);
+    sprintf(buf, "%shost: %s\n\r\n", buf, hostname);
+    write_or_die(fd, buf, strlen(buf));
+}
+
+//
+// Read the HTTP response and print it out
+//
+void client_print(int fd) {
+    char buf[MAXBUF];  
+    int n;
+    
+    // Read and display the HTTP Header 
+    n = readline_or_die(fd, buf, MAXBUF);
+    while (strcmp(buf, "\r\n") && (n > 0)) {
+	printf("Header: %s", buf);
+	n = readline_or_die(fd, buf, MAXBUF);
+	
+	// If you want to look for certain HTTP tags... 
+	// int length = 0;
+	//if (sscanf(buf, "Content-Length: %d ", &length) == 1) {
+	//    printf("Length = %d\n", length);
+	//}
+    }
+    
+    // Read and display the HTTP Body 
+    n = readline_or_die(fd, buf, MAXBUF);
+    while (n > 0) {
+	printf("%s", buf);
+	n = readline_or_die(fd, buf, MAXBUF);
+    }
+}
+
+int main(int argc, char *argv[]) {
+    char *host, *filename;
+    int port;
+    int clientfd;
+    
+    if (argc != 4) {
+	fprintf(stderr, "Usage: %s <host> <port> <filename>\n", argv[0]);
+	exit(1);
+    }
+    
+    host = argv[1];
+    port = atoi(argv[2]);
+    filename = argv[3];
+    
+    /* Open a single connection to the specified host and port */
+    clientfd = open_client_fd_or_die(host, port);
+    
+    client_send(clientfd, filename);
+    client_print(clientfd);
+    
+    close_or_die(clientfd);
+    
+    exit(0);
+}
diff --git a/concurrency-webserver/src/wserver.c b/concurrency-webserver/src/wserver.c
new file mode 100644
index 0000000..188abad
--- /dev/null
+++ b/concurrency-webserver/src/wserver.c
@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include "request.h"
+#include "io_helper.h"
+
+char default_root[] = ".";
+
+//
+// ./wserver [-d <basedir>] [-p <portnum>] 
+// 
+int main(int argc, char *argv[]) {
+    int c;
+    char *root_dir = default_root;
+    int port = 10000;
+    
+    while ((c = getopt(argc, argv, "d:p:")) != -1)
+	switch (c) {
+	case 'd':
+	    root_dir = optarg;
+	    break;
+	case 'p':
+	    port = atoi(optarg);
+	    break;
+	default:
+	    fprintf(stderr, "usage: wserver [-d basedir] [-p port]\n");
+	    exit(1);
+	}
+
+    // run out of this directory
+    chdir_or_die(root_dir);
+
+    // now, get to work
+    int listen_fd = open_listen_fd_or_die(port);
+    while (1) {
+	struct sockaddr_in client_addr;
+	int client_len = sizeof(client_addr);
+	int conn_fd = accept_or_die(listen_fd, (sockaddr_t *) &client_addr, (socklen_t *) &client_len);
+	request_handle(conn_fd);
+	close_or_die(conn_fd);
+    }
+    return 0;
+}
+
+
+    
+
+
+