/* 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"
// 接受請求,並處理
void accept_request(int clientsockfd);
// 無法處理請求,回寫400到client
void bad_request(int);
// 將文件內容發送到client
void cat(int client, FILE* fp);
// 不可以執行CGI程序,回寫500到client
void cannot_execute(int);
// 輸出錯誤信息
void error_die(const char *);
// 執行cgi程序
void execute_cgi(int, const char *, const char *, const char *);
// 從fd中讀取一行,並將讀取的'\r\n'和'\r'轉換爲'\n'
int get_line(int fd, char* buf, int bufsize);
// 返回200 OK給客戶端
void headers(int clientsockfd, const char * filename);
// 返回404狀態給客戶端
void not_found(int);
// 處理客戶端文件請求,發送404或200+文件內容到client
void serve_file(int client, const char* filename);
// 開啓soket監聽
int startup(u_short *);
// 返回501狀態給客戶端
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]; // 方法(請求類型)
char url[255]; // 請求的資源URL
char path[512]; // 請求資源的本地路徑
size_t i, j;
struct stat st;
int cgi = 0; /* becomes true if server decides this is a CGI program */
/* 爲真時,表示服務器需調用一個CGI程序 */
char *query_string = NULL;
// 1. 從客戶端連接請求數據包中讀取一行
numchars = get_line(client, buf, sizeof(buf));
// 2. 從讀取的數據中提取出請求類型
i = 0; j = 0;
while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
{
method[i] = buf[j];
i++; j++;
}
method[i] = '\0';
// 3. 判斷請求類型
if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
{
unimplemented(client); // 不支持請求類型,向客戶端返回501
return;
}
if (strcasecmp(method, "POST") == 0){
cgi = 1; // 如果是POST請求,調用cgi程序
}
// 4. 提取請求的資源URL
i = 0;
while (ISspace(buf[j]) && (j < sizeof(buf))){
j++; // 定位下一個非空格位置
}
while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
{
url[i] = buf[j];
i++; j++;
}
url[i] = '\0';
if (strcasecmp(method, "GET") == 0)
{
query_string = url; // 爲GET請求,查詢語句爲url
// 如果查詢語句中含義'?',查詢語句爲'?'字符後面部分
while ((*query_string != '?') && (*query_string != '\0')){
query_string++;
}
if (*query_string == '?')
{
cgi = 1;
*query_string = '\0'; // 從'?'處截斷,前半截爲url
query_string++;
}
}
// 5. 生成本地路徑
sprintf(path, "htdocs%s", url);
if (path[strlen(path) - 1] == '/'){
strcat(path, "index.html"); //如果請求url是以'/'結尾,則指定爲該目錄下的index.html文件
}
// 6. 判斷請求資源的狀態
if (stat(path, &st) == -1) {
// 從client中讀取,直到遇到兩個換行(起始行startline和首部header之間間隔)
while ((numchars > 0) && strcmp("\n", buf)){ /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
}
not_found(client); // 501
}
else
{
// 請求的是個目錄,指定爲該目錄下的index.html文件
if ((st.st_mode & S_IFMT) == S_IFDIR){
strcat(path, "/index.html");
}
// 請求的是一個可執行文件,作爲CGI程序
if ((st.st_mode & S_IXUSR) ||
(st.st_mode & S_IXGRP) ||
(st.st_mode & S_IXOTH) ){
cgi = 1;
}
// 判斷是執行一個CGI程序還是返回一個文件內容給客戶端
if (!cgi){
serve_file(client, path); //
}
else{
execute_cgi(client, path, method, query_string);
}
}
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];
// 向client回寫400狀態
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];
// 從resource中讀取一行
fgets(buf, sizeof(buf), resource);
// 將文件中的內容發送到客戶端
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];
// 向客戶端回寫500狀態,不可以執行CGI程序
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)
{
perror(sc); // 輸出錯誤信息
exit(1); // 退出程序
}
/********************************************************************//*
* @brief 執行一個CGI腳本.可能需要設置適當的環境變量.
* @prama client 客戶端socket文件描述符
* @prama path CGI 腳本路徑
* @prama method 請求類型
* @prama query_string 查詢語句
**********************************************************************/
void execute_cgi(int client, const char *path,
const char *method, const char *query_string)
{
char buf[1024];
int cgi_output[2]; // CGI程序輸出管道
int cgi_input[2]; // CGI程序輸入管道
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){
// 從client中讀取,直到遇到兩個換行
while ((numchars > 0) && strcmp("\n", buf)){ /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
}
}
else /* POST */
{
// 獲取請求主體的長度
numchars = get_line(client, buf, sizeof(buf));
while ((numchars > 0) && strcmp("\n", buf))
{
buf[15] = '\0';
if (strcasecmp(buf, "Content-Length:") == 0){
content_length = atoi(&(buf[16]));
}
numchars = get_line(client, buf, sizeof(buf));
}
if (content_length == -1) {
bad_request(client);
return;
}
}
// 向client回寫200 OK
sprintf(buf, "HTTP/1.0 200 OK\r\n");
send(client, buf, strlen(buf), 0);
// 創建兩個匿名管道
if (pipe(cgi_output) < 0) {
cannot_execute(client);
return;
}
if (pipe(cgi_input) < 0) {
cannot_execute(client);
return;
}
// 創建子進程,去執行CGI程序
if ( (pid = fork()) < 0 ) {
cannot_execute(client);
return;
}
if (pid == 0) /* child: CGI script */
{
char meth_env[255];
char query_env[255];
char length_env[255];
dup2(cgi_output[1], 1); //複製cgi_output[1](讀端)到子進程的標準輸出
dup2(cgi_input[0], 0); //複製cgi_input[0](寫端)到子進程的標準輸入
close(cgi_output[0]); //關閉多餘文件描述符
close(cgi_input[1]);
sprintf(meth_env, "REQUEST_METHOD=%s", method);
putenv(meth_env); // 添加一個環境變量
if (strcasecmp(method, "GET") == 0) {
sprintf(query_env, "QUERY_STRING=%s", query_string);
putenv(query_env);
}
else { /* POST */
sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
putenv(length_env);
}
// 執行CGI程序
execl(path, path, NULL);
exit(0); // 子進程退出
}
else
{ /* parent */
close(cgi_output[1]); // 關閉cgi_output讀端
close(cgi_input[0]); // 關閉cgi_input寫端
if (strcasecmp(method, "POST") == 0){
// 請求類型爲POST的時候,將POST數據包的主體entity-body部分
// 通過cgi_input[1](寫端)寫入到CGI的標準輸入
for (i = 0; i < content_length; i++) {
recv(client, &c, 1, 0);
write(cgi_input[1], &c, 1);
}
}
// 讀取CGI的標準輸出,發送到客戶端
while (read(cgi_output[0], &c, 1) > 0){
send(client, &c, 1, 0);
}
// 關閉多餘文件描述符
close(cgi_output[0]);
close(cgi_input[1]);
// 等待子進程結束
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;
while ((i < size - 1) && (c != '\n'))
{
// 從sock中讀取一個字節
n = recv(sock, &c, 1, 0);
/* DEBUG printf("%02X\n", c); */
if (n > 0)
{
// 將 \r\n 或 \r 轉換爲'\n'
if (c == '\r')
{
// 讀到了'\r'就再預讀一個字節
n = recv(sock, &c, 1, MSG_PEEK);
/* DEBUG printf("%02X\n", c); */
// 如果讀取到的是'\n',就讀取,否則c='\n'
if ((n > 0) && (c == '\n'))
recv(sock, &c, 1, 0);
else
c = '\n';
}
// 讀取數據放入buf
buf[i] = c;
i++;
}
else{
c = '\n';
}
}
buf[i] = '\0';
// 返回寫入buf的字節數
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 */
// 向客戶端回寫200應答
strcpy(buf, "HTTP/1.0 200 OK\r\n");
send(client, buf, strlen(buf), 0);
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];
// 向client回寫404狀態
sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");
send(client, buf, strlen(buf), 0);
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];
buf[0] = 'A'; buf[1] = '\0';
// 從client中讀取,直到遇到兩個換行(起始行start line和首部header的間隔)
while ((numchars > 0) && strcmp("\n", buf)){ /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
}
//
resource = fopen(filename, "r");
if (resource == NULL)
not_found(client); // 404錯誤
else
{
headers(client, filename); // 向客戶端回寫200 OK
cat(client, resource); // 將resource指向文件中的內容寫入client
}
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;
// 創建一個socket
httpd = socket(PF_INET, SOCK_STREAM, 0);
if (httpd == -1){
error_die("socket");
}
// 填寫綁定地址
memset(&name, 0, sizeof(name));
name.sin_family = AF_INET;
name.sin_port = htons(*port);
name.sin_addr.s_addr = htonl(INADDR_ANY);
// 綁定socket到指定地址
if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0){
error_die("bind");
}
// 如果採用隨機分配端口,獲取它
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);
}
// 監聽,等待連接
if (listen(httpd, 5) < 0)
error_die("listen");
// 返回正在監聽的文件描述符
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];
// 向client回寫501狀態
sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");
send(client, buf, strlen(buf), 0);
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; // 使用隨機端口
int client_sock = -1;
struct sockaddr_in client_name;
int client_name_len = sizeof(client_name);
pthread_t newthread;
// 啓動服務,監聽,等待連接
server_sock = startup(&port);
printf("httpd running on port %d\n", port);
while (1)
{
// 接受請求
client_sock = accept(server_sock,
(struct sockaddr *)&client_name,
&client_name_len);
if (client_sock == -1)
error_die("accept");
// 創建一個線程來處理請求
/* accept_request(client_sock); */
if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
perror("pthread_create");
}
// 關閉
close(server_sock);
return(0);
}
