C Tiny HTTPd源代码分析

void accept_request(int);//处理从套接字上监听到的一个 HTTP 请求
void bad_request(int);//返回给客户端这是个错误请求，400响应码
void cat(int, FILE *);//读取服务器上某个文件写到 socket 套接字
void cannot_execute(int);//处理发生在执行 cgi 程序时出现的错误
void error_die(const char *);//把错误信息写到 perror 
void execute_cgi(int, const char *, const char *, const char *);//运行cgi脚本，这个非常重要，涉及动态解析
int get_line(int, char *, int);//读取一行HTTP报文
void headers(int, const char *);//返回HTTP响应头
void not_found(int);//返回找不到请求文件
void serve_file(int, const char *);//调用 cat 把服务器文件内容返回给浏览器。
int startup(u_short *);//开启http服务，包括绑定端口，监听，开启线程处理链接
void unimplemented(int);//返回给浏览器表明收到的 HTTP 请求所用的 method 不被支持。

/* 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.
 * 1）注释掉#include <pthread.h>行。
 * 2）注释掉定义变量newthread的行。
 * 3）注释掉运行pthread_create（）的两行。
 * 4）取消注释运行accept_request（）的行。
 * 5）从Makefile中删除-lsocket。
 */
#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))
//函数说明：检查参数c是否为空格字符，
//也就是判断是否为空格(' ')、定位字符(' \t ')、CR(' \r ')、换行(' \n ')、垂直定位字符(' \v ')或翻页(' \f ')的情况。
//返回值：若参数c 为空白字符，则返回非 0，否则返回 0。

#define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"
//定义server名称

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 */
/**********************************************************************/
//接收客户端的连接，并读取请求数据
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;
    
    //获取一行HTTP报文数据
    numchars = get_line(client, buf, sizeof(buf));
    
    i = 0; j = 0;
    //对于HTTP报文来说，第一行的内容即为报文的起始行，格式为<method> <request-URL> <version>，每个字段用空白字符相连
    while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
    {
        //提取其中的请求方式是GET还是POST
        method[i] = buf[j];
        i++; j++;
    }
    method[i] = '\0';
    
    //函数说明：strcasecmp()用来比较参数s1 和s2 字符串，比较时会自动忽略大小写的差异。
    //返回值：若参数s1 和s2 字符串相同则返回0。s1 长度大于s2 长度则返回大于0 的值，s1 长度若小于s2 长度则返回小于0 的值。
    if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
    {
        //tinyhttp仅仅实现了GET和POST
        unimplemented(client);
        return;
    }
    
    //cgi为标志位，置1说明开启cgi解析
    if (strcasecmp(method, "POST") == 0)
        //如果请求方法为POST，需要cgi解析
        cgi = 1;
    
    i = 0;
    //将method后面的后边的空白字符略过
    while (ISspace(buf[j]) && (j < sizeof(buf)))
        j++;
        
    //继续读取request-URL
    while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
    {
        url[i] = buf[j];
        i++; j++;
    }
    url[i] = '\0';
    
    //如果是GET请求，url可能会带有?,有查询参数
    if (strcasecmp(method, "GET") == 0)
    {
        query_string = url;
        while ((*query_string != '?') && (*query_string != '\0'))
            query_string++;
        if (*query_string == '?')
        {
            //如果带有查询参数，需要执行cgi，解析参数，设置标志位为1
            cgi = 1;
            //将解析参数截取下来
            *query_string = '\0';
            query_string++;
        }
    }
    
    //以上已经将起始行解析完毕
    //url中的路径格式化到path
    sprintf(path, "htdocs%s", url);
    //如果path只是一个目录，默认设置为首页index.html
    if (path[strlen(path) - 1] == '/')
        strcat(path, "index.html");
        
    //函数定义:    int stat(const char *file_name, struct stat *buf);
    //函数说明:    通过文件名filename获取文件信息，并保存在buf所指的结构体stat中
    //返回值:     执行成功则返回0，失败返回-1，错误代码存于errno（需要include <errno.h>）
    if (stat(path, &st) == -1) {
        //假如访问的网页不存在，则不断的读取剩下的请求头信息，并丢弃即可
        while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
            numchars = get_line(client, buf, sizeof(buf));
            
        //最后声明网页不存在
        not_found(client);
    }
    else
    {
        //如果访问的网页存在则进行处理
        if ((st.st_mode & S_IFMT) == S_IFDIR)  //S_IFDIR代表目录
            //如果路径是个目录，那就将主页进行显示
            strcat(path, "/index.html");
            
        if ((st.st_mode & S_IXUSR) ||
            (st.st_mode & S_IXGRP) ||
            (st.st_mode & S_IXOTH)    )
            //S_IXUSR:文件所有者具可执行权限
            //S_IXGRP:用户组具可执行权限
            //S_IXOTH:其他用户具可读取权限  
            cgi = 1;
        if (!cgi)
            //将静态文件返回
            serve_file(client, path);
        else
            //执行cgi动态解析
            execute_cgi(client, path, method, query_string);
    }
    
    //因为http是面向无连接的，所以要关闭
    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];
    
    //发送400
    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 */
/**********************************************************************/
//读取服务器上某个文件写到 socket 套接字
void cat(int client, FILE *resource)
{
    //发送文件的内容
    char buf[1024];
    //读取文件到buf中
    fgets(buf, sizeof(buf), resource);
    while (!feof(resource))  //判断文件是否读取到末尾
    {
        //读取并发送文件内容
        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];
    
    //发送500
    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 */
/**********************************************************************/
//执行cgi动态解析
void execute_cgi(int client, const char *path,
                 const char *method, const char *query_string)
{
    char buf[1024];
    int cgi_output[2];  //声明的读写管道，切莫被名称给忽悠
    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';
    //如果是GET请求
    if (strcasecmp(method, "GET") == 0)
        while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers 读取并且丢弃头信息 */
            numchars = get_line(client, buf, sizeof(buf));
        
    //处理的请求为POST
    else    /* POST */
    {
        numchars = get_line(client, buf, sizeof(buf));
        //循环读取头信息找到Content-Length字段的值
        while ((numchars > 0) && strcmp("\n", buf))
        {
            buf[15] = '\0';  //目的是为了截取Content-Length:
            if (strcasecmp(buf, "Content-Length:") == 0)
                //"Content-Length: 15"
                content_length = atoi(&(buf[16]));  //获取Content-Length的值
            numchars = get_line(client, buf, sizeof(buf));
        }
        if (content_length == -1) {
            //错误请求
            bad_request(client);
            return;
        }
    }

    //返回正确响应码200
    sprintf(buf, "HTTP/1.0 200 OK\r\n");
    send(client, buf, strlen(buf), 0);
    
    //#include<unistd.h>
    //int pipe(int filedes[2]);
    //返回值：成功，返回0，否则返回-1。参数数组包含pipe使用的两个文件的描述符。fd[0]:读管道，fd[1]:写管道。
    //必须在fork()中调用pipe()，否则子进程不会继承文件描述符。
    //两个进程不共享祖先进程，就不能使用pipe。但是可以使用命名管道。
    //pipe(cgi_output)执行成功后，cgi_output[0]:读通道 cgi_output[1]:写通道，这就是为什么说不要被名称所迷惑
    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;
    }
    
    //fork出一个子进程运行cgi脚本
    if (pid == 0)  /* child: CGI script 子进程: 运行CGI 脚本 */
    {
        char meth_env[255];
        char query_env[255];
        char length_env[255];
        
        dup2(cgi_output[1], 1);  //1代表着stdout，0代表着stdin，将系统标准输出重定向为cgi_output[1]
        dup2(cgi_input[0], 0);  //将系统标准输入重定向为cgi_input[0]，这一点非常关键，cgi程序中用的是标准输入输出进行交互
        close(cgi_output[0]);  //关闭了cgi_output中的读通道
        close(cgi_input[1]);  //关闭了cgi_input中的写通道
        
        //CGI标准需要将请求的方法存储环境变量中，然后和cgi脚本进行交互
        //存储REQUEST_METHOD
        sprintf(meth_env, "REQUEST_METHOD=%s", method);
        putenv(meth_env);
        if (strcasecmp(method, "GET") == 0) {
            //存储QUERY_STRING
            sprintf(query_env, "QUERY_STRING=%s", query_string);
            putenv(query_env);
        }
        else {   /* POST */
            //存储CONTENT_LENGTH
            sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
            putenv(length_env);
        }
        
        // 表头文件#include<unistd.h>
        // 定义函数
        // int execl(const char * path,const char * arg,....);
        // 函数说明
        // execl()用来执行参数path字符串所代表的文件路径，接下来的参数代表执行该文件时传递过去的argv(0)、argv[1]……，最后一个参数必须用空指针(NULL)作结束。
        // 返回值
        // 如果执行成功则函数不会返回，执行失败则直接返回-1，失败原因存于errno中。
        execl(path, path, NULL);  //执行CGI脚本
        exit(0);
    } else {    /* parent 父进程 */
        close(cgi_output[1]);  //关闭了cgi_output中的写通道，注意这是父进程中cgi_output变量和子进程要区分开
        close(cgi_input[0]);  //关闭了cgi_input中的读通道
        
        if (strcasecmp(method, "POST") == 0)
            for (i = 0; i < content_length; i++) {
                //开始读取POST中的内容
                recv(client, &c, 1, 0);
                //将数据发送给cgi脚本
                write(cgi_input[1], &c, 1);
            }
        
        //读取cgi脚本返回数据
        while (read(cgi_output[0], &c, 1) > 0)
            //发送给浏览器
            send(client, &c, 1, 0);

        //运行结束关闭
        close(cgi_output[0]);
        close(cgi_input[1]);
        
        //定义函数：pid_t waitpid(pid_t pid, int * status, int options);
        //函数说明：waitpid()会暂时停止目前进程的执行, 直到有信号来到或子进程结束.
        //如果在调用wait()时子进程已经结束, 则wait()会立即返回子进程结束状态值. 子进程的结束状态值会由参数status 返回,
        //而子进程的进程识别码也会一快返回.
        //如果不在意结束状态值, 则参数status 可以设成NULL. 参数pid 为欲等待的子进程识别码, 其他数值意义如下：
        //1、pid<-1 等待进程组识别码为pid 绝对值的任何子进程.
        //2、pid=-1 等待任何子进程, 相当于wait().
        //3、pid=0 等待进程组识别码与目前进程相同的任何子进程.
        //4、pid>0 等待任何子进程识别码为pid 的子进程.
        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) */
/**********************************************************************/
//解析一行http报文
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);
                /* DEBUG printf("%02X\n", c); */
                if ((n > 0) && (c == '\n'))
                    recv(sock, &c, 1, 0);
                else
                    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 */
/**********************************************************************/
void headers(int client, const char *filename)
{
    char buf[1024];
    (void)filename;  /* could use filename to determine file type */
    
    //发送HTTP头
    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];
    //返回404
    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 */
/**********************************************************************/
//将请求的文件发送回浏览器客户端
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 将HTTP请求头读取并丢弃 */
        numchars = get_line(client, buf, sizeof(buf));
    
    //打开文件
    resource = fopen(filename, "r");
    if (resource == NULL)
        //如果文件不存在，则返回not_found
        not_found(client);
    else
    {
        //添加HTTP头
        headers(client, filename);
        //并发送文件内容
        cat(client, resource);
    }
    
    //关闭文件句柄
    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 */
/**********************************************************************/
//启动服务端。开启http服务，包括绑定端口，监听，开启线程处理链接
int startup(u_short *port)
{
    int httpd = 0;
    struct sockaddr_in name;
    
    //设置http socket
    httpd = socket(PF_INET, SOCK_STREAM, 0);
    if (httpd == -1)
        error_die("socket");
    memset(&name, 0, sizeof(name));
    name.sin_family = AF_INET;  // AF_INET  Supported address families -> Internet IP Protocol
    name.sin_port = htons(*port);
    name.sin_addr.s_addr = htonl(INADDR_ANY);
    
    //绑定端口
    if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
        error_die("bind");
  
    /*动态分配一个端口 */
    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);
    }
    //监听连接
    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 */
/**********************************************************************/
//返回给浏览器表明收到的 HTTP 请求所用的 method 不被支持。
void unimplemented(int client)
{
    char buf[1024];
    
    //发送501说明相应方法没有实现
    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;  // unsigned short
    int client_sock = -1;
    struct sockaddr_in client_name;
    int 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);
        //接受客户端连接
        client_sock = accept(server_sock,
                           (struct sockaddr *)&client_name,
                           &client_name_len);
                           
        if (client_sock == -1)
            error_die("accept");
            
        accept_request(client_sock);
        // 启动线程处理新的连接。 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
        // if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
        //     perror("pthread_create");
    }
    
    //关闭server socketss
    close(server_sock);
    
    return(0);
}

all: httpd

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

clean:
    rm httpd

#!/usr/local/bin/perl -Tw

use strict;
use CGI;

my($cgi) = new CGI;

print $cgi->header;
my($color) = "blue";
$color = $cgi->param('color') if defined $cgi->param('color');

print $cgi->start_html(-title => uc($color),
                       -BGCOLOR => $color);
print $cgi->h1("This is $color");
print $cgi->end_html;

#!/usr/bin/env php

<?php
echo "<html>";
echo "<head>";
echo "<title>POST</title>";
echo "</head>";
echo "<body>";
echo "<CENTER>Today is:</CENTER>";
echo "<CENTER><B>";
echo date('Y-m-d H:i:s');
echo "</B></CENTER>";
echo "</body></html>";

#!/bin/bash

echo "Content-Type: text/html"
echo
echo "<HTML><BODY>"
echo "<CENTER>Today is:</CENTER>"
echo "<CENTER><B>"
date
echo "</B></CENTER>"
echo "</BODY></HTML>"

#!/usr/bin/python
#coding:utf-8
import sys,os
length = os.getenv('CONTENT_LENGTH')
 
if length:
    postdata = sys.stdin.read(int(length))
    print "Content-type:text/html\n"
    print '<html>'
    print '<head>'
    print '<title>POST</title>'
    print '</head>'
    print '<body>'
    print '<h2> POST data </h2>'
    print '<ul>'
    for data in postdata.split('&'):
        print  '<li>'+data+'</li>'
    print '</ul>'
    print '</body>'
    print '</html>'
     
else:
    print "Content-type:text/html\n"
    print 'no found'

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
    int sockfd;
    int len;
    struct sockaddr_in address;
    int result;
    char ch = 'A';
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = inet_addr("127.0.0.1");
    address.sin_port = htons(9734);
    len = sizeof(address);
    result = connect(sockfd, (struct sockaddr *)&address, len);
    
    if (result == -1)
    {
        perror("oops: client1");
        exit(1);
    }
    write(sockfd, &ch, 1);
    read(sockfd, &ch, 1);
    printf("char from server = %c\n", ch);
    close(sockfd);
    exit(0);
}