简易Web服务器
老早就学习了Web服务器， 那是在《深入理解计算机系统》后面有个例子是有关Web服务器的，并给了一个简单的例子。
例子包含3个文件，csapp.h, csapp.c, tiny.c。现将tiny.c列出来。
/*
* tiny.c - A simple, iterative HTTP/1.0 Web server that uses the
* GET method to serve static and dynamic content
*/
#include "csapp.h"
void doit(int fd);
void read_requesthdrs(rio_t *rp);
int parse_uri(char *uri, char *filename, char *cgiargs);
void server_static(int fd, char *filename, int filesize);
void get_filetype(char *filename, char *filetype);
void server_dynamic(int fd, char *filename, char *cgiargs);
void clienterror(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg);
int main(int argc, char **argv)
{
int listenfd, connfd, port, clientlen;
struct sockaddr_in clientaddr;
/* Check command line args */
if (argc != 2)
{
fprintf(stderr, "usage:%s <port>\n", argv[0]);
exit(1);
}
port = atoi(argv[1]);
listenfd = Open_listenfd(port);
while (1)
{
clientlen = sizeof(clientaddr);
connfd = Accept(listenfd, (SA *)&clientaddr, &clientlen);
doit(connfd);
Close(connfd);
}
}
void doit(int fd)
{
int is_static;
struct stat sbuf;
char buf[MAXLINE], method[MAXLINE], uri[MAXLINE], version[MAXLINE];
char filename[MAXLINE], cgiargs[MAXLINE];
rio_t rio;
/* Read request line and headers */
Rio_readinitb(&rio, fd);
Rio_readlineb(&rio, buf, MAXLINE);
sscanf(buf, "%s %s %s", method, uri, version);
if (strcasecmp(method, "GET"))
{
clienterror(fd, method, "501", "Not Implemented",
"Tiny does not implement this method");
return ;
}
read_requesthdrs(&rio);
/* Parse URI from GET request */
is_static = parse_uri(uri, filename, cgiargs);
if (stat(filename, &sbuf) < 0)
{
clienterror(fd, filename, "404", "Not found", "Tiny couldn't find this file");
return;
}
if (is_static)
{
if( !(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode))
{
clienterror(fd, filename, "403", "FOrbidden", "tiny couldn't read the file");
return ;
}
server_static(fd, filename, sbuf.st_size);
}
else
{
if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode))
{
clienterror(fd, filename, "403", "Forbidden", "Tiny couldn't run the CGI program");
return ;
}
server_dynamic(fd, filename, cgiargs);
}
}
void clienterror(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg)
{
char buf[MAXLINE], body[MAXBUF];
/* Build the HTTP response body */
sprintf(body, "<html><title>Tiny Error</title>");
sprintf(body, "%s<body bgcolor=""ffffff"">\r\bn", body);
sprintf(body, "%s%s: %s\r\n",body, errnum, shortmsg);
sprintf(body, "%s<p>%s:%s\r\n", body, longmsg, cause);
sprintf(body, "%s<hr><em>The Tiny Web server</em>\r\n", body);
/* Print the HTTP response */
sprintf(buf, "HTTP 1.0 %s %s \r\n", errnum, shortmsg);
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Content-type:text/html\r\n");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "content-lengt:%d\r\n\r\n", (int)strlen(body));
Rio_writen(fd, buf, strlen(buf));
Rio_writen(fd, body, strlen(body));
}
void read_requesthdrs(rio_t *rp)
{
char buf[MAXLINE];
Rio_readlineb(rp, buf, MAXLINE);
while (strcmp(buf, "\r\n"))
{
Rio_readlineb(rp, buf, MAXLINE);
printf("%s", buf);
}
return;
}
int parse_uri(char *uri, char *filename, char *cgiargs)
{
char *ptr;
if (!strstr(uri, "cgi-bin")) /* static content */
{
strcpy(cgiargs, "");
strcpy(filename, ".");
strcat(filename, uri);
if (uri[strlen(uri)-1] == '/')
{
strcat(filename, "home.html");
}
return 1;
}
else /* dynamic content */
{
ptr = index(uri, '?');
if (ptr)
{
strcpy(cgiargs, ptr + 1);
*ptr = '\0';
}
else
{
strcpy(cgiargs, "");
}
strcpy(filename, ".");
strcat(filename, uri);
return 0;
}
}
void server_static(int fd, char *filename, int filesize)
{
int srcfd;
char *srcp, filetype[MAXLINE], buf[MAXBUF];
/* Send response headers to client */
get_filetype(filename, filetype);
sprintf(buf, "HTTP/1.0 200 OK\r\n");
sprintf(buf, "%sServer: Tiny Web Server\r\n", buf);
sprintf(buf, "%sContent-length:%d\r\n", buf, filesize);
sprintf(buf, "%sContent_type:%s\r\n\r\n", buf, filetype);
Rio_writen(fd, buf, strlen(buf));
/* Send response body to client */
srcfd = Open(filename, O_RDONLY, 0);
srcp = Mmap(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0);
Close(srcfd);
Rio_writen(fd, srcp, filesize);
Munmap(srcp, filesize);
}
/*
* GET -derive file type from file name
*/
void 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 server_dynamic(int fd, char *filename, char *cgiargs)
{
char buf[MAXLINE], *emptylist[] = { };
/* Return first part of HTTP response */
sprintf(buf, "HTTP/1.0 200 OK\r\n");
Rio_writen(fd, buf, strlen(buf));
sprintf(buf, "Server:Tiny web Server \r\n");
Rio_writen(fd, buf, strlen(buf));
if (Fork() == 0) /* child */
{
/* Real server would set all CGI vars here */
setenv("QUERY_STRING", cgiargs, 1);
Dup2(fd, STDOUT_FILENO);
Execve(filename, emptylist, environ);
}
Wait(NULL);
}
现在我知道了Web服务器到底是什么概念了，它和普通的服务器有什么区别了。。。
Web服务器比如http服务器它就是实现了http协议的服务器，当然我们也可以自定义自己的协议。
但是底层都是使用tcp/ip协议来传输数据的。