/* J. David's webserver */
/* This is a simple webserver.
* Created November 1999 by J. David Blackstone.
* CSE 4344 (Network concepts), Prof. Zeigler
* University of Texas at Arlington
*/
/* This program compiles for Sparc Solaris 2.6.
* To compile for Linux:
* 1) Comment out the #include <pthread.h> line.
* 2) Comment out the line that defines the variable newthread.
* 3) Comment out the two lines that run pthread_create().
* 4) Uncomment the line that runs accept_request().
* 5) Remove -lsocket from the Makefile.
*/
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <ctype.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <pthread.h>
#include <sys/wait.h>
#include <stdlib.h>
#define ISspace(x) isspace((int)(x))
#define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"
void accept_request(int);
void bad_request(int);
void cat(int, FILE *);
void cannot_execute(int);
void error_die(const char *);
void execute_cgi(int, const char *, const char *, const char *);
int get_line(int, char *, int);
void headers(int, const char *);
void not_found(int);
void serve_file(int, const char *);
int startup(u_short *);
void unimplemented(int);
/**********************************************************************/
/* A request has caused a call to accept() on the server port to
* return. Process the request appropriately.
* Parameters: the socket connected to the client */
/**********************************************************************/
void accept_request(int client)
{
char buf[1024];
int numchars;
char method[255];
char url[255];
char path[512];
size_t i, j;
struct stat st;
int cgi = 0; /* becomes true if server decides this is a CGI program */
char *query_string = NULL;
/*得到请求的第一行*/
numchars = get_line(client, buf, sizeof(buf));
i = 0; j = 0;
/*把客户端的请求方法存到 method 数组*/
while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
{
method[i] = buf[j];
i++; j++;
}
method[i] = '\0';
/*如果既不是 GET 又不是 POST 则无法处理 */
if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
{
unimplemented(client);
return;
}
/* POST 的时候开启 cgi */
if (strcasecmp(method, "POST") == 0)
cgi = 1;
/*读取 url 地址*/
i = 0;
while (ISspace(buf[j]) && (j < sizeof(buf)))
j++;
while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
{
/*存下 url */
url[i] = buf[j];
i++; j++;
}
url[i] = '\0';
/*处理 GET 方法*/
if (strcasecmp(method, "GET") == 0)
{
/* 待处理请求为 url */
query_string = url;
while ((*query_string != '?') && (*query_string != '\0'))
query_string++;
/* GET 方法特点，? 后面为参数*/
if (*query_string == '?')
{
/*开启 cgi */
cgi = 1;
*query_string = '\0';
query_string++;
}
}
/*格式化 url 到 path 数组，html 文件都在 htdocs 中*/
sprintf(path, "htdocs%s", url);
/*默认情况为 index.html */
if (path[strlen(path) - 1] == '/')
strcat(path, "index.html");
/*根据路径找到对应文件 */
if (stat(path, &st) == -1) {
/*把所有 headers 的信息都丢弃*/
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
/*回应客户端找不到*/
not_found(client);
}
else
{
/*如果是个目录，则默认使用该目录下 index.html 文件*/
if ((st.st_mode & S_IFMT) == S_IFDIR)
strcat(path, "/index.html");
if ((st.st_mode & S_IXUSR) || (st.st_mode & S_IXGRP) || (st.st_mode & S_IXOTH) )
cgi = 1;
/*不是 cgi,直接把服务器文件返回，否则执行 cgi */
if (!cgi)
serve_file(client, path);
else
execute_cgi(client, path, method, query_string);
}
/*断开与客户端的连接（HTTP 特点：无连接）*/
close(client);
}
/**********************************************************************/
/* Inform the client that a request it has made has a problem.
* Parameters: client socket */
/**********************************************************************/
void bad_request(int client)
{
char buf[1024];
/*回应客户端错误的 HTTP 请求 */
sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "Content-type: text/html\r\n");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "\r\n");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "<P>Your browser sent a bad request, ");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "such as a POST without a Content-Length.\r\n");
send(client, buf, sizeof(buf), 0);
}
/**********************************************************************/
/* Put the entire contents of a file out on a socket. This function
* is named after the UNIX "cat" command, because it might have been
* easier just to do something like pipe, fork, and exec("cat").
* Parameters: the client socket descriptor
* FILE pointer for the file to cat */
/**********************************************************************/
void cat(int client, FILE *resource)
{
char buf[1024];
/*读取文件中的所有数据写到 socket */
fgets(buf, sizeof(buf), resource);
while (!feof(resource))
{
send(client, buf, strlen(buf), 0);
fgets(buf, sizeof(buf), resource);
}
}
/**********************************************************************/
/* Inform the client that a CGI script could not be executed.
* Parameter: the client socket descriptor. */
/**********************************************************************/
void cannot_execute(int client)
{
char buf[1024];
/* 回应客户端 cgi 无法执行*/
sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-type: text/html\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<P>Error prohibited CGI execution.\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
/* Print out an error message with perror() (for system errors; based
* on value of errno, which indicates system call errors) and exit the
* program indicating an error. */
/**********************************************************************/
void error_die(const char *sc)
{
/*出错信息处理 */
perror(sc);
exit(1);
}
/**********************************************************************/
/* Execute a CGI script. Will need to set environment variables as
* appropriate.
* Parameters: client socket descriptor
* path to the CGI script */
/**********************************************************************/
void execute_cgi(int client, const char *path, const char *method, const char *query_string)
{
char buf[1024];
int cgi_output[2];
int cgi_input[2];
pid_t pid;
int status;
int i;
char c;
int numchars = 1;
int content_length = -1;
buf[0] = 'A'; buf[1] = '\0';
if (strcasecmp(method, "GET") == 0)
/*把所有的 HTTP header 读取并丢弃*/
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
else /* POST */
{
/* 对 POST 的 HTTP 请求中找出 content_length */
numchars = get_line(client, buf, sizeof(buf));
while ((numchars > 0) && strcmp("\n", buf))
{
/*利用 \0 进行分隔 */
buf[15] = '\0';
/* HTTP 请求的特点*/
if (strcasecmp(buf, "Content-Length:") == 0)
content_length = atoi(&(buf[16]));
numchars = get_line(client, buf, sizeof(buf));
}
/*没有找到 content_length */
if (content_length == -1) {
/*错误请求*/
bad_request(client);
return;
}
}
/* 正确，HTTP 状态码 200 */
sprintf(buf, "HTTP/1.0 200 OK\r\n");
send(client, buf, strlen(buf), 0);
/* 建立管道*/
if (pipe(cgi_output) < 0) {
/*错误处理*/
cannot_execute(client);
return;
}
/*建立管道*/
if (pipe(cgi_input) < 0) {
/*错误处理*/
cannot_execute(client);
return;
}
if ((pid = fork()) < 0 ) {
/*错误处理*/
cannot_execute(client);
return;
}
if (pid == 0) /* child: CGI script */
{
char meth_env[255];
char query_env[255];
char length_env[255];
/* 把 STDOUT 重定向到 cgi_output 的写入端 */
dup2(cgi_output[1], 1);
/* 把 STDIN 重定向到 cgi_input 的读取端 */
dup2(cgi_input[0], 0);
/* 关闭 cgi_input 的写入端 和 cgi_output 的读取端 */
close(cgi_output[0]);
close(cgi_input[1]);
/*设置 request_method 的环境变量*/
sprintf(meth_env, "REQUEST_METHOD=%s", method);
putenv(meth_env);
if (strcasecmp(method, "GET") == 0) {
/*设置 query_string 的环境变量*/
sprintf(query_env, "QUERY_STRING=%s", query_string);
putenv(query_env);
}
else { /* POST */
/*设置 content_length 的环境变量*/
sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
putenv(length_env);
}
/*用 execl 运行 cgi 程序*/
execl(path, path, NULL);
exit(0);
} else { /* parent */
/* 关闭 cgi_input 的读取端 和 cgi_output 的写入端 */
close(cgi_output[1]);
close(cgi_input[0]);
if (strcasecmp(method, "POST") == 0)
/*接收 POST 过来的数据*/
for (i = 0; i < content_length; i++) {
recv(client, &c, 1, 0);
/*把 POST 数据写入 cgi_input，现在重定向到 STDIN */
write(cgi_input[1], &c, 1);
}
/*读取 cgi_output 的管道输出到客户端，该管道输入是 STDOUT */
while (read(cgi_output[0], &c, 1) > 0)
send(client, &c, 1, 0);
/*关闭管道*/
close(cgi_output[0]);
close(cgi_input[1]);
/*等待子进程*/
waitpid(pid, &status, 0);
}
}
/**********************************************************************/
/* Get a line from a socket, whether the line ends in a newline,
* carriage return, or a CRLF combination. Terminates the string read
* with a null character. If no newline indicator is found before the
* end of the buffer, the string is terminated with a null. If any of
* the above three line terminators is read, the last character of the
* string will be a linefeed and the string will be terminated with a
* null character.
* Parameters: the socket descriptor
* the buffer to save the data in
* the size of the buffer
* Returns: the number of bytes stored (excluding null) */
/**********************************************************************/
int get_line(int sock, char *buf, int size)
{
int i = 0;
char c = '\0';
int n;
/*把终止条件统一为 \n 换行符，标准化 buf 数组*/
while ((i < size - 1) && (c != '\n'))
{
/*一次仅接收一个字节*/
n = recv(sock, &c, 1, 0);
/* DEBUG printf("%02X\n", c); */
if (n > 0)
{
/*收到 \r 则继续接收下个字节，因为换行符可能是 \r\n */
if (c == '\r')
{
/*使用 MSG_PEEK 标志使下一次读取依然可以得到这次读取的内容，可认为接收窗口不滑动*/
n = recv(sock, &c, 1, MSG_PEEK);
/* DEBUG printf("%02X\n", c); */
/*但如果是换行符则把它吸收掉*/
if ((n > 0) && (c == '\n'))
recv(sock, &c, 1, 0);
else
c = '\n';
}
/*存到缓冲区*/
buf[i] = c;
i++;
}
else
c = '\n';
}
buf[i] = '\0';
/*返回 buf 数组大小*/
return(i);
}
/**********************************************************************/
/* Return the informational HTTP headers about a file. */
/* Parameters: the socket to print the headers on
* the name of the file */
/**********************************************************************/
void headers(int client, const char *filename)
{
char buf[1024];
(void)filename; /* could use filename to determine file type */
/*正常的 HTTP header */
strcpy(buf, "HTTP/1.0 200 OK\r\n");
send(client, buf, strlen(buf), 0);
/*服务器信息*/
strcpy(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/html\r\n");
send(client, buf, strlen(buf), 0);
strcpy(buf, "\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
/* Give a client a 404 not found status message. */
/**********************************************************************/
void not_found(int client)
{
char buf[1024];
/* 404 页面 */
sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");
send(client, buf, strlen(buf), 0);
/*服务器信息*/
sprintf(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/html\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<HTML><TITLE>Not Found</TITLE>\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<BODY><P>The server could not fulfill\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "your request because the resource specified\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "is unavailable or nonexistent.\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "</BODY></HTML>\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
/* Send a regular file to the client. Use headers, and report
* errors to client if they occur.
* Parameters: a pointer to a file structure produced from the socket
* file descriptor
* the name of the file to serve */
/**********************************************************************/
void serve_file(int client, const char *filename)
{
FILE *resource = NULL;
int numchars = 1;
char buf[1024];
/*读取并丢弃 header */
buf[0] = 'A'; buf[1] = '\0';
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
/*打开 sever 的文件*/
resource = fopen(filename, "r");
if (resource == NULL)
not_found(client);
else
{
/*写 HTTP header */
headers(client, filename);
/*复制文件*/
cat(client, resource);
}
fclose(resource);
}
/**********************************************************************/
/* This function starts the process of listening for web connections
* on a specified port. If the port is 0, then dynamically allocate a
* port and modify the original port variable to reflect the actual
* port.
* Parameters: pointer to variable containing the port to connect on
* Returns: the socket */
/**********************************************************************/
int startup(u_short *port)
{
int httpd = 0;
struct sockaddr_in name;
/*建立 socket */
httpd = socket(PF_INET, SOCK_STREAM, 0);
if (httpd == -1)
error_die("socket");
memset(&name, 0, sizeof(name));
name.sin_family = AF_INET;
name.sin_port = htons(*port);
name.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
error_die("bind");
/*如果当前指定端口是 0，则动态随机分配一个端口*/
if (*port == 0) /* if dynamically allocating a port */
{
int namelen = sizeof(name);
if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
error_die("getsockname");
*port = ntohs(name.sin_port);
}
/*开始监听*/
if (listen(httpd, 5) < 0)
error_die("listen");
/*返回 socket id */
return(httpd);
}
/**********************************************************************/
/* Inform the client that the requested web method has not been
* implemented.
* Parameter: the client socket */
/**********************************************************************/
void unimplemented(int client)
{
char buf[1024];
/* HTTP method 不被支持*/
sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");
send(client, buf, strlen(buf), 0);
/*服务器信息*/
sprintf(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/html\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<HTML><HEAD><TITLE>Method Not Implemented\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "</TITLE></HEAD>\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<BODY><P>HTTP request method not supported.\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "</BODY></HTML>\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
int main(void)
{
int server_sock = -1;
u_short port = 0;
int client_sock = -1;
struct sockaddr_in client_name;
int client_name_len = sizeof(client_name);
pthread_t newthread;
/*在对应端口建立 httpd 服务*/
server_sock = startup(&port);
printf("httpd running on port %d\n", port);
while (1)
{
/*套接字收到客户端连接请求*/
client_sock = accept(server_sock,(struct sockaddr *)&client_name,&client_name_len);
if (client_sock == -1)
error_die("accept");
/*派生新线程用 accept_request 函数处理新请求*/
/* accept_request(client_sock); */
if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
perror("pthread_create");
}
close(server_sock);
return(0);
}
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