在实际开发中经常用到web框架，比如Servlet，SpringBoot等，这些开发框架提高了我们的开发效率，节省了开发时间。但是这会令我们技术人员处于浮云之上，看不到其本质。说实话，Java语言那么流行，其本质是运行在JRE虚拟机上的，而JRE是用C/C++语言开发的。与其说java跨平台，不如说是因为在不同平台上各自实现JRE，从而屏蔽了java语言直接与不同平台打交道。http协议广泛应用，也是基于TCP协议之上的封装。本节博主将带领大家用C语言在Linux环境下开发HTTP服务器，支持浏览器下载和浏览文件。另外还使用TCP协议开发了服务端和客户端来实现服务端监听客户端连接，然后向其发送一首唐诗。

目录

1.HTTP服务器

1.1 源码

1.2 效果

2.TCP服务器和客户端

2.1 源码

2.1 效果

---

1.HTTP服务器

1.1 源码

头文件：

#pragma once
#include <pthread.h>

//线程参数结构
struct ThreadParam {
    pthread_t tid;
    int fd;
    int epfd;
};

int initListenFd(unsigned short port);

int epoolRun(int lfd);

void* acceptClient(void *);

void* recvHttpRequest(void *);

int parseRequestLine(int cfd, const char *line);

int sendFile(int cfd, const char *fileName);

int sendHeadMsg(int cfd, int status, const char *descr, const char *type, int length);

const char *getFileType(const char *name);

int sendDir(int cfd, const char*dirName);

int hex2dec (char c);

char dec2hex (short int c);

void urlDecode(char* from, char *to);

源文件

#include "HttpServer.h"
#include <arpa/inet.h>
#include <stdio.h> 
#include <stdlib.h>
#include <sys/epoll.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include <sys/sendfile.h>
#include <dirent.h>
#include <ctype.h>

int initListenFd(unsigned short port) {
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == lfd) {
        perror("scoket");
        return -1;
    }
    int opt = -1;
    int ret = setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    if (-1 == ret) {
        perror("setsockopt");
        return -1;
    }
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = INADDR_ANY;
    ret = bind(lfd, (const struct sockaddr *)&addr, sizeof(addr));
    if (-1 == ret) {
        perror("bind");
        return -1;
    }
    ret = listen(lfd, 128);
    if (-1 == ret) {
        perror("listen");
        return -1;
    }
    return lfd;
}

int epoolRun(int lfd) {
    int epfd = epoll_create(1);
    if (-1 == epfd) {
        perror("epoll_create");
        return -1;
    }
    struct epoll_event ev;
    ev.data.fd = lfd;
    ev.events = EPOLLIN;
    int ret = epoll_ctl(epfd, EPOLL_CTL_ADD, lfd, &ev);
    if (-1 == ret) {
        perror("epoll_ctl");
        return -1;
    }
    struct epoll_event evs[2048];
    int maxwait = sizeof(evs) / sizeof(struct epoll_event);
    while (1) {
        int num = epoll_wait(epfd, evs, maxwait, -1);
        for (int i = 0; i <= num; i++) {
            int fd = evs[i].data.fd;
            pthread_t tid;
            struct ThreadParam *param = 
                (struct ThreadParam *)malloc(sizeof(struct ThreadParam));
            param->fd = fd;
            param->epfd = epfd;
            param->tid = tid;
            if (fd == lfd) {
                pthread_create(&tid, NULL, acceptClient, param);
                pthread_detach(tid);
            }
            else {
                pthread_create(&tid, NULL, recvHttpRequest, param);
                pthread_detach(tid);
            }
        }
    }
    
    return 0;
}

void* acceptClient(void *arg) {
    struct ThreadParam *param = (struct ThreadParam *)arg;
    if (!param) {
        return NULL;
    }
    int lfd = param->fd;
    int epfd = param->epfd;
    int cfd = accept(lfd, NULL, NULL);
    if (-1 == cfd) {
        perror("accept");
        return NULL;
    }
    int flag = fcntl(cfd, F_GETFL);
    flag |= O_NONBLOCK;
    fcntl(cfd, F_SETFL, flag);
    struct epoll_event ev;
    ev.data.fd = cfd;
    ev.events = EPOLLIN | EPOLLET; //cfd边缘非阻塞模式，效率最高
    int ret = epoll_ctl(epfd, EPOLL_CTL_ADD, cfd, &ev);
    if (-1 == cfd) {
        perror("epoll_ctl");
    }
    free(param);
    param = NULL;
    printf("accept thread %ld\n", pthread_self());
    return NULL;
}

void* recvHttpRequest(void *arg) {
    struct ThreadParam *param = (struct ThreadParam *)arg;
    char buf[8192] = {0};
    int len = 0;
    int total = 0;
    char tmpBuf[1024] = {0};
    if (!param) {
        return NULL;
    }
    int cfd = param->fd;
    int epfd = param->epfd;
    while ((len = recv(cfd, tmpBuf, sizeof(tmpBuf), 0)) > 0) {
        if (total + len < sizeof(buf)) {
            memcpy(buf + total, tmpBuf, len);
        }
        total += len;
    }
    if (-1 == len && errno == EAGAIN && total > 0) { //接收数据完毕
        //解析http协议
        char *pt = strstr(buf, "\r\n");
        int reqLen = pt - buf;
        buf[reqLen] = '\0';
        parseRequestLine(cfd, buf);
    }
    else if (0 == len) { //客户端断开了连接
        epoll_ctl(epfd, EPOLL_CTL_DEL, cfd, NULL);
        close(cfd);
    }
    else {
        perror("recv");
    }
    free(param);
    param = NULL;
    printf("client thread %ld\n", pthread_self());
    return NULL;
}

int parseRequestLine(int cfd, const char *line) {
    char method[32] = {0};
    char path[2048] = {0};
    char decodePath[1024] = {0};
    char protocol[128] = {0};
    //sscanf解析格式化字符串
    sscanf(line, "%[^ ] %[^ ] %s", method, path, protocol);
    printf("method: %s, path: %s protocol: %s\n", method, path, protocol);
    if (0 != strcasecmp(method, "get")) {
        return -1;
    }
    urlDecode(path, decodePath);
    //http中/代表服务端工作的资源根目录
    char *file = NULL;
    if (0 == strcmp(decodePath, "/")) {
        file = ".";
    }
    else {
        file = decodePath + 1;
    }
    struct stat st;
    int ret = stat(file, &st);
    if (-1 == ret) {
        //回复404页面
        sendHeadMsg(cfd, 404, "Not Found", getFileType(".html"), -1); //-1表示不知道长度，让浏览器自己解析去
        sendFile(cfd, "404.html");
        return 0;
    }
    if (S_ISDIR(st.st_mode)) {
        sendHeadMsg(cfd, 200, "OK", getFileType(".html"), -1);
        sendDir(cfd, file);
    }
    else {
        sendHeadMsg(cfd, 200, "OK", getFileType(file), st.st_size);
        sendFile(cfd, file);
    }

    return 0;
}

int sendFile(int cfd, const char *fileName) {
    //读一部分数据，发送一部分数据，因为tcp是面向连接的流式的
    int fd = open(fileName, O_RDONLY);
    assert(fd > 0);
#if 0
    while (1) {
        char buf[1024];
        int len = read(fd, buf, sizeof(buf));
        if (len > 0) {
            send(cfd, buf, len, 0);
            usleep(20); //减轻接收端压力
        }
        else if (0 == len) {
            break;
        }
        else {
            perror("read");
        }
    }
#endif
#if 1
    off_t len = 0;
    int size = lseek(fd, 0, SEEK_END);
    lseek(fd, 0, SEEK_SET);
    while (len < size) {
        int ret = sendfile(cfd, fd, &len, size - len);
        printf("ret value %d \n", ret);
        if (-1 == ret) {
            if (EAGAIN == errno) {
                printf("no data\n");
                perror("sendfile");
            }
            else {
                printf("client quit \n");
                break;
            }
        }
        
    }
#endif
    return 0;
}

int sendHeadMsg(int cfd, int status, const char *descr, const char *type, int length) {
    char buf[8192] = {0};
    int offset = 0;
    int ret = sprintf(buf + offset, "http/1.1 %d %s\r\n", status, descr);
    offset += ret;
    ret = sprintf(buf + offset, "content-type: %s\r\n", type);
    offset += ret;
    ret = sprintf(buf + offset, "content-length: %d\r\n\r\n", length);
    offset += ret;
    send(cfd, buf, offset, 0);
    return 0;
}

const char *getFileType(const char *name) {
    const char* dot = strrchr(name, '.');
    if (NULL == dot) {
        return "text/palin; charset=utf-8";
    }
    if (0 == strcasecmp(dot, ".html")) {
        return "text/html; charset=utf-8";
    }
    if (0 == strcasecmp(dot, ".png")) {
        return "image/png; charset=utf-8";
    }
    if (0 == strcasecmp(dot, ".txt")) {
        return "text/palin; charset=utf-8";
    }
    // ...
    return "application/octet-stream; charset=utf-8";
}

int sendDir(int cfd, const char*dirName) {
    char buf[2048] = {0};
    int len = 0;
    int ret = sprintf(buf + len, "<html><head><title>%s</title><body><table>", dirName);
    len += ret;
    struct dirent** namelist = NULL;
    int num = scandir(dirName, &namelist, NULL, alphasort);
    for (int i = 0; i < num; i++) {
        char * name = namelist[i]->d_name;
        struct stat st;
        char path[1024] = {0};
        sprintf(path, "%s/%s", dirName, name);
        stat(path, &st);
        if (S_ISDIR(st.st_mode)) {
            if (!strcmp(".", name) || !strcmp("..", name)) {
                continue;
            }
            ret = sprintf(buf + len, "<tr><td><a href=\"%s/\" style=\"font-size:20px\">%s</a>    </td><td>%ld</td></tr>", \
                        name, name, st.st_size);
        }
        else {
            ret = sprintf(buf + len, "<tr><td><a href=\"%s\" style=\"font-size:20px\">%s</a>    </td><td>%ld</td></tr>",
                        name, name, st.st_size);
        }
        len += ret;
        send(cfd, buf, len, 0);
        len = 0;
        memset(buf, 0x00, sizeof(buf));
        free(namelist[i]);
    }
    len = sprintf(buf, "</table></head></body></html>");
    send(cfd, buf, len, 0);
    free(namelist);
    return 0;
}

int hex2dec (char c) {
    if ('0' <= c && c <= '9') return c - '0';
    else if ('a' <= c && c <= 'f') return c - 'a' + 10;
    else if ('A' <= c && c <= 'F') return c - 'A' + 10;
    return 0;
}

char dec2hex (short int c) {
    if (0 <= c && c <= 9) return c + '0';
    else if (10 <= c && c <= 15) return c + 'A' - 10;
    return 0;
}

void urlDecode(char* org, char *obj) {
    if (!org || !obj) {
        return;
    }
    //isxdigit:判断字符是否是十六进制字符
    for (; *org != '\0'; ++org, ++obj) {
        if ('%' == org[0] && isxdigit(org[1]) && isxdigit(org[2])) {
            *obj = hex2dec(org[1]) * 16 + hex2dec(org[2]);
            org += 2;
        }
        else {
            *obj = *org;
        }
    }
}

主程序：

#include <stdio.h>
#include <unistd.h>
#include "HttpServer.h"

int main(int argc, char** argv) {
    unsigned short int port;
    if (argc < 3) {
        printf("program {port} {path}\n");
        return -1;
    }
    sscanf(argv[1], "%hu", &port);
    printf("begin start http server, listen %d ...\n", port);
    //修改进程的工作目录
    chdir(argv[2]);
    int lfd = initListenFd(port);
    epoolRun(lfd);

    return 0;
}

Makefile 编译脚本：

app: httpServer tcpServer tcpClient

#说明：$^代表依赖项
httpServer: CommonUtil.c HttpServer.c main.c
	gcc -g $^ -o httpServer -lpthread 

tcpServer: CommonUtil.c TcpServer.c
	gcc -g $^ -o tcpServer

tcpClient: CommonUtil.c TcpClient.c
	gcc -g $^ -o tcpClient

clean:
	-rm httpServer tcpServer tcpClient -f

1.2 效果

 

 

 

 

2.TCP服务器和客户端

2.1 源码

头文件：

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

int isLittleEndian();

int readn(int fd, char* buf, int len);

int writen(int fd, char *buf, int len);

源文件

 #include <strings.h>
#include <arpa/inet.h>
#include <stdio.h> 
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include "CommonUtil.h"

static const char* _s_showMsg [] = {
    "次北固山下",
    "【作者】王湾 【朝代】唐",
    "客路青山外，行舟绿水前。",
    "潮平两岸阔，风正一帆悬。",
    "海日生残夜，江春入旧年。",
    "乡书何处达？归雁洛阳边。"
};

static void sendMsg(int fd, const char *data, int len) {
    char *buf = (char *)malloc(sizeof(int) + len);
    int nlen = len;
    if (isLittleEndian()) {
        nlen = htonl(len);
    }
    memcpy(buf, &nlen, sizeof(int));
    memcpy(buf + sizeof(int), data, len);
    printf("发送数据长度:: [%d] 内容:: [%s]\n", len, data);
    writen(fd, buf, sizeof(int) + len);
    if (buf) {
        free(buf);
    }
}

static int startTcpServer(unsigned short port)
{
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == lfd) {
        perror("scoket");
        return -1;
    }
    int opt = -1;
    int ret = setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
    if (-1 == ret) {
        perror("setsockopt");
        return -1;
    }
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = INADDR_ANY;
    ret = bind(lfd, (const struct sockaddr *)&addr, sizeof(addr));
    if (-1 == ret) {
        perror("bind");
        return -1;
    }
    ret = listen(lfd, 128);
    if (-1 == ret) {
        perror("listen");
        return -1;
    }
    struct sockaddr_in client;
    socklen_t client_addrlen = sizeof(client);
     printf("port %d, wait client accept ...\n", port);
    int connfd = accept(lfd, (struct sockaddr*)(&client), &client_addrlen);
    if (connfd < 0) {
        perror("accept");
        return -1;
    }
    printf("connect client info: addr = %s, port = %d\n",
            inet_ntoa(client.sin_addr), ntohs(client.sin_port));
    int lineNum = sizeof(_s_showMsg) / sizeof(_s_showMsg[0]);
    for (int i = 0; i < lineNum; i++) {
        sendMsg(connfd, _s_showMsg[i], strlen(_s_showMsg[i]));
        usleep(1000 * 100); //此处为了减轻客户端压力
    }
    printf("我活干完了，数据已经全部发送到客户端！\n");
    getchar();
    close(connfd);
    close(lfd);

    return 1;
}

int main(int argc, char**argv) {
    if (argc < 2) {
        printf("a.out {port}\n");
        return -1;
    }
    unsigned short port;
    sscanf(argv[1], "%hu", &port);
    startTcpServer(port);
    return 0;
}

#include <arpa/inet.h>
#include <stdio.h> 
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>
#include "CommonUtil.h"

static void recvMsg(int fd, char **data, int *len) {
   int nlen = 0;
   int ret = readn(fd, (char*)&nlen, sizeof(int));
   *len = nlen;
   if (isLittleEndian()) {
        *len = ntohl(nlen);
   }
   char *tmp = (char *)malloc(*len + 1);
   readn(fd, tmp, *len);
   tmp[*len] = '\0';
   *data = tmp;
}

static int startTcpClient(unsigned short port)
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);    
	assert(-1 != sockfd);
	//指定服务器的ip和端口
	struct sockaddr_in saddr;  
    memset(&saddr, 0, sizeof(saddr)); 
    saddr.sin_family = AF_INET;   
    saddr.sin_port = htons(port);    
    //saddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    inet_pton(sockfd, "127.0.0.1", &saddr.sin_addr.s_addr);
    //作为客户端不需要指定端口，系统自动给客户端设置端口，连接上后直接收发数据
    printf("begin connect port %d\n", port);
    int ret = connect(sockfd, (struct sockaddr*)&saddr, sizeof(saddr));   
    if (-1 == ret) {
        perror("connect");
        return 0;
    }
    while(1)    
    {               
    	char *buff = NULL;          
        int ret = 0;
        recvMsg(sockfd, &buff, &ret);
        if (-1 == ret) {
            perror("read");
            break;
        }
        else if (0 == ret) {
            perror("server quit ");
            break;
        }
        else {
            if (buff) {
                printf("接收数据长度:: [%d] 内容:: [%s]\n", ret, buff);
                free(buff);
            }
        }
        printf("\r\n------------------------------\n\r");
        sleep(rand() % 10);
     }
    close(sockfd);    
    exit(0); 
}

int main(int argc, char**argv) {
    if (argc < 2) {
        printf("a.out {port}\n");
        return -1;
    }
    unsigned short port;
    sscanf(argv[1], "%hu", &port);
    startTcpClient(port);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include "CommonUtil.h"

int isLittleEndian() {
    static unsigned short data = 0x1234;
    if (*((char*)&data) == 0x34) {
        return 1;
    }
    else {
        return 0;
    }
}


int readn(int fd, char* buf, int len) {
    int nleft = len;
    int nread = 0;
    char *pbuf = buf;
    while (nleft > 0) {
        nread = read(fd, pbuf, nleft);
        if (-1 == nread) {
            perror("read");
            return -1;
        }
        else if (0 == nread) {
            return len - nleft;
        }
        pbuf += nread;
        nleft -= nread;
    }
    return len;
}

int writen(int fd, char *buf, int len) {
    int nleft = len;
    int nwrite = 0;
    char *pbuf = buf;
    while (nleft > 0) {
        nwrite = write(fd, pbuf, nleft);
        if (-1 == nwrite) {
            perror("write");
            return -1;
        }
        else if (0 == nwrite) {
            continue;
        }
        pbuf += nwrite;
        nleft -= nwrite;
    }
    return len;
}

编译脚本：

app: httpServer tcpServer tcpClient

#说明：$^代表依赖项
httpServer: CommonUtil.c HttpServer.c main.c
	gcc -g $^ -o httpServer -lpthread 

tcpServer: CommonUtil.c TcpServer.c
	gcc -g $^ -o tcpServer

tcpClient: CommonUtil.c TcpClient.c
	gcc -g $^ -o tcpClient

clean:
	-rm httpServer tcpServer tcpClient -f

2.1 效果

源码下载路径如下：
https://download.csdn.net/download/hsy12342611/87183336 

只有平时多接触底层编程才能体会到一些技术的本质，做技术不能被表面的虚幻所迷惑，要从本质上去理解一些东西，好的，今天就到这里了，该去休息了。