//很感慨，以前看着很吃力的代码现在看着觉得并不难理解，很懊恼自己当时的阅读代码方法，

/* 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.
    1. Comment out the line that defines the variable newthread.
    1. Comment out the two lines that run pthread_create().
    1. Uncomment the line that runs accept_request().
    1. 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>

//宏定义，是否是空格 #define ISspace(x) isspace((int)(x))

#define SERVER_STRING “Server: jdbhttpd/0.1.0\r\n”

//每次收到请求，创建一个线程来处理接受到的请求

//把client_sock转成地址作为参数传入pthread_create void accept_request(void* arg);

//错误请求 void bad_request(int);

//读取文件 void cat(int, FILE*);

//无法执行 void cannot_execute(int);

//错误输出 void error_die(const char*);

//执行cig脚本 void execute_cgi(int, const char*, const char*, const char*);

//得到一行数据,只要发现c为\n,就认为是一行结束，如果读到\r,再用MSG_PEEK的方式读入一个字符，如果是\n，从socket用读出 //如果是下个字符则不处理，将c置为\n，结束。如果读到的数据为0中断，或者小于0，也视为结束，c置为\n int get_line(int, char*, int);

//返回http头 void headers(int, const char*);

//没有发现文件 void not_found(int);

//如果不是CGI文件，直接读取文件返回给请求的http客户端 void serve_file(int, const char*);

//开启tcp连接，绑定端口等操作 int startup(u_short*);

//如果不是Get或者Post，就报方法没有实现 void unimplemented(int);

// Http请求，后续主要是处理这个头 // // GET / HTTP/1.1 // Host: 192.168.0.23:47310 // Connection: keep-alive // Upgrade-Insecure-Requests: 1 // User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36 // Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/; q = 0.8 // Accept - Encoding: gzip, deflate, sdch // Accept - Language : zh - CN, zh; q = 0.8 // Cookie: __guid = 179317988.1576506943281708800.1510107225903.8862; monitor_count = 5 //

// POST / color1.cgi HTTP / 1.1 // Host: 192.168.0.23 : 47310 // Connection : keep - alive // Content - Length : 10 // Cache - Control : max - age = 0 // Origin : http ://192.168.0.23:40786 // Upgrade - Insecure - Requests : 1 // User - Agent : Mozilla / 5.0 (Windows NT 6.1; WOW64) AppleWebKit / 537.36 (KHTML, like Gecko) Chrome / 55.0.2883.87 Safari / 537.36 // Content - Type : application / x - www - form - urlencoded // Accept : text / html, application / xhtml + xml, application / xml; q = 0.9, image / webp, /;q=0.8 // Referer: http://192.168.0.23:47310/ // Accept-Encoding: gzip, deflate // Accept-Language: zh-CN,zh;q=0.8 // Cookie: __guid=179317988.1576506943281708800.1510107225903.8862; monitor_count=281 // Form Data // color=gray

/*********************************************************************/ / 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(void arg) { //socket int client = (intptr_t)arg; 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;//query_string 指针指向 url 中 ？ 后面的 GET 参数

    //根据上面的Get请求，可以看到这边就是取第一行 //这边都是在处理第一条http信息 //”GET / HTTP/1.1\n” numchars = get_line(client, buf, sizeof(buf)); i = 0; j = 0;

    //第一行字符串提取Get while (!ISspace(buf[j]) && (i < sizeof(method) - 1)) { method[i] = buf[j]; i++; j++; } //结束 method[i] = ‘\0’;

    //判断是Get还是Post if (strcasecmp(method, “GET”) && strcasecmp(method, “POST”)) { unimplemented(client); return; }

    //如果是POST，cgi置为1 if (strcasecmp(method, “POST”) == 0) cgi = 1;

    i = 0; //跳过空格 while (ISspace(buf[j]) && (j < sizeof(buf))) j++;

    //得到 “/” 注意：如果你的http的网址为http://192.168.0.23:47310/index.html // 那么你得到的第一条http信息为GET /index.html HTTP/1.1，那么 // 解析得到的就是/index.html while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf))) { url[i] = buf[j]; i++; j++; } url[i] = ‘\0’;

    //判断Get请求 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++; } }

    //路径 sprintf(path, “htdocs%s”, url);

    //默认地址，解析到的路径如果为/，则自动加上index.html if (path[strlen(path) - 1] == ‘/’) strcat(path, “index.html”);

    //获得文件信息 if (stat(path, &st) == -1) { //把所有http信息读出然后丢弃 while ((numchars > 0) && strcmp(“\n”, buf)) /* read & discard headers */ numchars = get_line(client, buf, sizeof(buf));

     //没有找到
 not_found(client);

    } else { if ((st.st_mode & S_IFMT) == S_IFDIR) strcat(path, “/index.html”); //如果你的文件默认是有执行权限的，自动解析成cgi程序，如果有执行权限但是不能执行，会接受到报错信号 if ((st.st_mode & S_IXUSR) || (st.st_mode & S_IXGRP) || (st.st_mode & S_IXOTH)) cgi = 1; if (!cgi) //接读取文件返回给请求的http客户端 serve_file(client, path); else //执行cgi文件 execute_cgi(client, path, method, query_string); } //执行完毕关闭socket 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, “

    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 */

/**********************************************************************/

//得到文件内容，发送 void cat(int client, FILE* resource) { char buf[1024];

fgets(buf, sizeof(buf), resource);
//循环读
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];

    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, “

    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) { //缓冲区 char buf[1024];

//2根管道
int cgi_output[2];
int cgi_input[2];

//进程pid和状态
pid_t pid;
int status;

int i;
char c;

//读取的字符数
int numchars = 1;

//http的content_length
int content_length = -1;

//默认字符
buf[0] = 'A'; buf[1] = '\0';

//忽略大小写比较字符串
if (strcasecmp(method, "GET") == 0)
    //读取数据，把整个header都读掉，以为Get写死了直接读取index.html，没有必要分析余下的http信息了
    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))
    {
        //如果是POST请求，就需要得到Content-Length，Content-Length：这个字符串一共长为15位，所以
        //取出头部一句后，将第16位设置结束符，进行比较
        //第16位置为结束
        buf[15] = '\0';
        if (strcasecmp(buf, "Content-Length:") == 0)
            //内存从第17位开始就是长度，将17位开始的所有字符串转成整数就是content_length
            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);
//建立output管道
if (pipe(cgi_output) < 0) {
    cannot_execute(client);
    return;
}

//建立input管道
if (pipe(cgi_input) < 0) {
    cannot_execute(client);
    return;
}
//       fork后管道都复制了一份，都是一样的
//       子进程关闭2个无用的端口，避免浪费             
//       ×<------------------------->1    output
//       0<-------------------------->×   input 

//       父进程关闭2个无用的端口，避免浪费             
//       0<-------------------------->×   output
//       ×<------------------------->1    input
//       此时父子进程已经可以通信


//fork进程，子进程用于执行CGI
//父进程用于收数据以及发送子进程处理的回复数据
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];

    //子进程输出重定向到output管道的1端
    dup2(cgi_output[1], 1);
    //子进程输入重定向到input管道的0端
    dup2(cgi_input[0], 0);

    //关闭无用管道口
    close(cgi_output[0]);
    close(cgi_input[1]);

    //CGI环境变量
    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);
    }
    //替换执行path
    execl(path, path, NULL);
    //int m = execl(path, path, NULL);
    //如果path有问题，例如将html网页改成可执行的，但是执行后m为-1
    //退出子进程，管道被破坏，但是父进程还在往里面写东西，触发Program received signal SIGPIPE, Broken pipe.
    exit(0);
}
else {    /* parent */

//关闭无用管道口 close(cgi_output[1]); close(cgi_input[0]); if (strcasecmp(method, “POST”) == 0) for (i = 0; i < content_length; i++) { //得到post请求数据，写到input管道中，供子进程使用 recv(client, &c, 1, 0); write(cgi_input[1], &c, 1); } //从output管道读到子进程处理后的信息，然后send出去 while (read(cgi_output[0], &c, 1) > 0) send(client, &c, 1, 0);

    //完成操作后关闭管道
    close(cgi_output[0]);
    close(cgi_input[1]);

    //等待子进程返回
    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) / /*********************************************************************/

//得到一行数据,只要发现c为\n,就认为是一行结束，如果读到\r,再用MSG_PEEK的方式读入一个字符，如果是\n，从socket用读出 //如果是下个字符则不处理，将c置为\n，结束。如果读到的数据为0中断，或者小于0，也视为结束，c置为\n 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')
        {
            //偷窥一个字节，如果是\n就读走
            n = recv(sock, &c, 1, MSG_PEEK);
            /* DEBUG printf("%02X\n", c); */
            if ((n > 0) && (c == '\n'))
                recv(sock, &c, 1, 0);
            else
                //不是\n（读到下一行的字符）或者没读到，置c为\n 跳出循环,完成一行读取
                c = '\n';
        }
        buf[i] = c;
        i++;
    }
    else
        c = '\n';
}
buf[i] = '\0';

return(i);

}

/*********************************************************************/ / Return the informational HTTP headers about a file. / / Parameters: the socket to print the headers on

  •         the name of the file */

/**********************************************************************/

//加入http的headers 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. / //

//如果资源没有找到得返回给客户端下面的信息 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 */

/**********************************************************************/

//如果不是CGI文件，直接读取文件返回给请求的http客户端 void serve_file(int client, const char* filename) { FILE* resource = NULL; int numchars = 1; char buf[1024];

//默认字符
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");
if (resource == NULL)
    not_found(client);
else
{
    headers(client, filename);
    cat(client, resource);
}
fclose(resource);

}

// / 主要完成了以下工作 1，创建套接字 2，绑定套接字 3，提供随机端口 修改了port指针 4，监听套接字 / // int startup(u_short* port) { int httpd = 0; struct sockaddr_in name;//此数据结构用做bind、connect、recvfrom、sendto等函数的参数，指明地址信息。

httpd = socket(PF_INET, SOCK_STREAM, 0);/*1、参数domain指明通信域，如PF_INET(IPv4),type 指明通信类型，最常用的如SOCK_STREAM(面向连接可靠方式，  比如TCP)、SOCK_DGRAM(非面向连接的非可靠方式，比如
    UDP)等。  SOCK_STREAM 是数据流, 一般是tcp / ip协议的编程, SOCK_DGRAM分是数据抱, 是udp协议网络编程。
    3、参数protocol指定需要使用的协议。虽然可以对同一个协议  家族(protocol family)(或者说通信域(domain))指定不同的协议参数
    但是通常只有一个。对于TCP参数可指定为IPPROTO_TCP, 对于  UDP可以用IPPROTO_UDP。你不必显式制定这个参数，使用0则根据前
    两个参数使用默认的协议。　*/
if (httpd == -1)
    error_die("socket");

memset(&name, 0, sizeof(name));//对name初始化
name.sin_family = AF_INET;//IPV4
name.sin_port = htons(*port);//主机字节顺序转换为网络字节顺序
name.sin_addr.s_addr = htonl(INADDR_ANY);//监听本机所有IP

//绑定socket
if (bind(httpd, (struct sockaddr*) & name, sizeof(name)) < 0)
    error_die("bind");

//如果端口没有设置，提供个随机端口
if (*port == 0)  /* if dynamically allocating a port */
{
    socklen_t  namelen = sizeof(name);
    if (getsockname(httpd, (struct sockaddr*) & name, &namelen) == -1)
        error_die("getsockname");
    *port = ntohs(name.sin_port);//网络字节顺序转换为主机字节顺序
}

//对socket进行监听
//5代表内核维护一个队列跟踪这些完成的连接但服务器还没有接受处理
//或者正在进行的连接的最大长度

//如无错误发生，listen()返回0。否则的话，返回-1 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 / /*********************************************************************/

//如果方法没有实现，就返回此信息 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);

}

/**********************************************************************/

/* main函数主要做了以下工作， 1，网络初始化，通过startup实现。 2，循环侦听客户端连接，通过accept实现。 3，实现侦听到连接后启动线程处理连接，通过pthread_create启动线程，accept_request处理连接。 4，关闭网络，用close函数实现。 */ int main(void) {

int server_sock = -1;
u_short port = 0;
int client_sock = -1;
struct sockaddr_in client_name;

//这边要为socklen_t类型
socklen_t client_name_len = sizeof(client_name);
pthread_t newthread;

server_sock = startup(&port);
printf("httpd running on port %d\n", port);

while (1)
{
    //接受请求，函数原型
    //#include <sys/types.h>
    //#include <sys/socket.h>  
    //int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
    client_sock = accept(server_sock,
        (struct sockaddr*) & client_name,
        &client_name_len);
    if (client_sock == -1)
        error_die("accept");
    /* accept_request(client_sock); */

     //每次收到请求，创建一个线程来处理接受到的请求
     //把client_sock转成地址作为参数传入pthread_create
    /*第一个参数为指向线程标识符的指针。
    第二个参数用来设置线程属性。
    第三个参数是线程运行函数的起始地址。
    最后一个参数是运行函数的参数。*/
    if (pthread_create(&newthread, NULL, (void*)accept_request, (void*)(intptr_t)client_sock) != 0)
        perror("pthread_create");
}

close(server_sock);

return(0);

}