TinyHttp源碼解讀

標籤：c   web伺服器   源碼   tinyhttp   

tinyhttp是一個最簡單的web伺服器，實現了web伺服器的基本原理。代碼全部使用C語言開發，只有500多行，閱讀代碼，可以瞭解web伺服器的基本原理。

下載串連：http://sourceforge.net/projects/tinyhttpd/

下載後，編譯時間會遇到問題。在Makefile中，執行編譯指令碼為：

gcc -W -Wall -lsocket -lpthread -o httpd httpd.c

其中lsocket是不需要的，因為作者開發時用的Linux版本和我不同，我使用了Ubuntu Server，不需要這個選線。

-lpthread應該替換為-pthread，具體原因參考這裡。

還有一些警告，是因為參數類型的問題。

在我編譯後，運行時發現首頁打不開。使用GDB調試，斷點加在fork後的子進程，在GDB模式要設定:set follow-fork mode child，這樣執行fork後GDB才會調試子進程。最後才發現index.html有執行許可權，需要去掉這個許可權才行。

<span style="font-size:14px;">/* 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))//check if 'x' is a white-space#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;//record the information about the file int cgi = 0;      /* becomes true if server decides this is a CGI                    * program */ char *query_string = NULL; numchars = get_line(client, buf, sizeof(buf)); i = 0; j = 0; while (!ISspace(buf[j]) && (i < sizeof(method) - 1))//'method' contains the http method(GET/POST) {  method[i] = buf[j];  i++; j++; } method[i] = '\0'; //compares the characters ignoring case of character if (strcasecmp(method, "GET") && strcasecmp(method, "POST")) {  unimplemented(client);  return; } if (strcasecmp(method, "POST") == 0)  cgi = 1; i = 0; while (ISspace(buf[j]) && (j < sizeof(buf)))//skip the Header  j++; while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))//copy the URL to 'url' {  url[i] = buf[j];  i++; j++; } url[i] = '\0'; if (strcasecmp(method, "GET") == 0) {  query_string = url;  while ((*query_string != '?') && (*query_string != '\0'))   query_string++;  if (*query_string == '?')  {   cgi = 1;   *query_string = '\0';   query_string++;  } } sprintf(path, "htdocs%s", url);//write 'url' to path and add 'htdocs' at the head of path if (path[strlen(path) - 1] == '/')  strcat(path, "index.html"); if (stat(path, &st) == -1) {//check if the file exist or not  while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */   numchars = get_line(client, buf, sizeof(buf));  not_found(client);//file not exist } else//file exist {  if ((st.st_mode & S_IFMT) == S_IFDIR)//a directory   strcat(path, "/index.html");  if ((st.st_mode & S_IXUSR) ||//check the permission owner, group user or other users      (st.st_mode & S_IXGRP) ||      (st.st_mode & S_IXOTH)    )   cgi = 1;  if (!cgi)//not a CIG   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]; 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]; fgets(buf, sizeof(buf), resource); while (!feof(resource))//feof: check end-of-file indicator {  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]; 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); 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];//pipe to communicate between parent and child 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)  while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */   numchars = get_line(client, buf, sizeof(buf)); else    /* POST */ {  numchars = get_line(client, buf, sizeof(buf));  while ((numchars > 0) && strcmp("\n", buf))  {   buf[15] = '\0';//set buf[15]='\0' to compare with "Content-Length:"   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;  } } sprintf(buf, "HTTP/1.0 200 OK\r\n"); send(client, buf, strlen(buf), 0);//send respond status if (pipe(cgi_output) < 0) {  cannot_execute(client);  return; } if (pipe(cgi_input) < 0) {  cannot_execute(client);  return; } 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);//redirect cgi_output[1] to standard output  dup2(cgi_input[0], 0);//redirect cgi_input[0] to standard input  close(cgi_output[0]);//the parent process use cgi_output[0] to input data  close(cgi_input[1]);//the parent process use cig_input[1] to output data  sprintf(meth_env, "REQUEST_METHOD=%s", method);  putenv(meth_env);  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);//and value of environment variables  }  execl(path, path, NULL);//execute the CGI program  exit(0); } else {    /* parent */  close(cgi_output[1]);  close(cgi_input[0]);  if (strcasecmp(method, "POST") == 0)   for (i = 0; i < content_length; i++) {    recv(client, &c, 1, 0);    write(cgi_input[1], &c, 1);//pass the para to child process   }  while (read(cgi_output[0], &c, 1) > 0)//read the child process result   send(client, &c, 1, 0);  close(cgi_output[0]);  close(cgi_input[1]);  waitpid(pid, &status, 0);//wait for child process until it ends }}/**********************************************************************//* 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')) {  n = recv(sock, &c, 1, 0);  /* DEBUG printf("%02X\n", c); */  if (n > 0)  {   if (c == '\r')   {    n = recv(sock, &c, 1, MSG_PEEK);//peek, in fact don't read the data.    /* DEBUG printf("%02X\n", c); */    if ((n > 0) && (c == '\n'))//if terminated with CRLF     recv(sock, &c, 1, 0);    else     c = '\n';   }   buf[i] = c;   i++;  }  else   c = '\n'; } buf[i] = '\0';// the buffer end with null  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 */ 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]; 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'; while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */  numchars = get_line(client, buf, sizeof(buf)); resource = fopen(filename, "r");//open the file with read permission if (resource == NULL)  not_found(client); else {  headers(client, filename);//send headers to client  cat(client, resource);//send content to 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; httpd = socket(PF_INET, SOCK_STREAM, 0);//PF_INET's value is same with AF_INET. PF stands for Protocol family if (httpd == -1)  error_die("socket"); memset(&name, 0, sizeof(name)); name.sin_family = AF_INET;// AF stands for Address family 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"); if (*port == 0)  /* if dynamically allocating a port */ {  int namelen = sizeof(name);  if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)//get the current socket   error_die("getsockname");  *port = ntohs(name.sin_port);//set the port number } if (listen(httpd, 5) < 0)  error_die("listen"); 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]; 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; int client_sock = -1; struct sockaddr_in client_name; int client_name_len = sizeof(client_name); pthread_t newthread; server_sock = startup(&port);//get the server socket printf("httpd running on port %d\n", port); while (1) {  client_sock = accept(server_sock,                       (struct sockaddr *)&client_name,                       &client_name_len);//wait for a connection  if (client_sock == -1)   error_die("accept"); /* accept_request(client_sock); */ if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)//create a thread to process the connection   perror("pthread_create"); } close(server_sock); return(0);}</span>

TinyHttp源碼解讀