websocket的实现
本文的websocket实现基于单线程Reactor网络模型的代码实现
初步了解websocket（必读）:参考连接
websocekt的实现基于http，数据传输与处理过程也很类似：基于reactor的http服务器
websocket握手
websocket基于TCP连接，但为了保证客户端的合法性，会在三次握手后再进行两次握手：
- 三次握手后，该连接进入handshark握手阶段
- handshark成功后，进入Tranmission阶段
- websocket关闭连接
因此，服务器需要为每个连接定义一个状态机，取出该TCP连接后，根据连接当前状态做相应操作：
// 状态机
enum {
WS_HANDSHARK = 0,
WS_TRANMISSION = 1,
WS_END = 2,
};
struct ntyevent {
int fd;
int events;
void *arg;
int (*callback)(int fd, int events, void *arg);
int status;
char buffer[BUFFER_LENGTH];
int length;
long last_active;
int status_machine; // fd与事件绑定，fd的状态就是事件的状态
};
// 根据不同的状态做相应处理
int websocket_request(struct ntyevent *ev) {
if (ev->status_machine == WS_HANDSHARK) {
ev->status_machine = WS_TRANMISSION;
handshark(ev);
} else if (ev->status_machine == WS_TRANMISSION) {
transmission(ev);
} else {
}
printf("websocket_request --> %d\n", ev->status_machine);
}
服务器取出TCP连接后，都会进入WS_HANDSHARK状态，接下来就是websocket的两次握手：
- 是listenfd监听到新连接后，触发其回调函数accept_cb(),将这个事件的状态设置为WS_HANDSHARK，并将新连接connfd加入epoll
- 客户端紧接着再进行一次握手，触发该connfd的可读事件，调用其回调函数recv_cb(),recv_cb()调用websocket_request()进行处理，将其状态更改为WS_TRANMISSION，调用handshark()进行握手,handshark()处理流程为：
- 解析websocket：读取buff（客户端发送的握手消息如下图），获取其中的WebSocket-Key(base64编码)，与服务器的GUID做一个拼接
- Hash拼接后的字符串，再base64得到一个最终值，并发送给客户端
- 客户端验证这个值，验证成功就真正连接了
- 接下来该连接上的数据传输都在WS_TRANMISSION状态进行
websocekt握手消息,和http很类似
- 客户端发送：
GET / HTTP/1.1
Host: 192.168.232.128:8888
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36
Upgrade: websocket
Origin: null
Sec-WebSocket-Version: 13
Accept-Encoding: gzip, deflate
Accept-Language: zh-TW,zh;q=0.9,en-US;q=0.8,en;q=0.7
Sec-WebSocket-Key: QWz1vB/77j8J8JcT/qtiLQ==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
- 服务端返回：
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
websocket握手过程的实现handshark():
int handshark(struct ntyevent *ev) {
char linebuf[1024] = {0};
int idx = 0;
char sec_data[128] = {0};
char sec_accept[32] = {0};
do {
memset(linebuf, 0, 1024);
idx = readline(ev->buffer, idx, linebuf);
if (strstr(linebuf, "Sec-WebSocket-Key")) { // 读WebSocket-Key
//linebuf: Sec-WebSocket-Key: QWz1vB/77j8J8JcT/qtiLQ==
strcat(linebuf, GUID);
//linebuf:
//Sec-WebSocket-Key: QWz1vB/77j8J8JcT/qtiLQ==258EAFA5-E914-47DA-95CA-C5AB0DC85B11
SHA1(linebuf + WEBSOCK_KEY_LENGTH, strlen(linebuf + WEBSOCK_KEY_LENGTH), sec_data); // openssl
base64_encode(sec_data, strlen(sec_data), sec_accept);
memset(ev->buffer, 0, BUFFER_LENGTH);
ev->length = sprintf(ev->buffer, "HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n\r\n", sec_accept);
printf("ws response : %s\n", ev->buffer);
break;
}
} while((ev->buffer[idx] != '\r' || ev->buffer[idx+1] != '\n') && idx != -1 );
return 0;
}
websocket协议格式
数据传输状态，weobsocket协议的消息以数据帧（Data Framing）的形式发送，包括包头和包体两部分，其中包头又分为三部分：
- 第一部分：前两个byte，如控制websocket连接关闭的FIN（类似TCP连接，为1就说明这是最后一个包）、是否启用密文传输的MASK（为1启用）、数据长度Payload len
- 第二部分：由于第一部分的Payload len只有7个bit，最大为127，当包体数据较多时，无法表示，就会将第一部分的Payload len置为126，启用扩展的poyload length；如果还是无法表示数据的长度，将Payload len置为127，再加上第三块poyload length一起表示
- 第三部分：Masking-key，长度4byte，用于加密明文。（用Masking-key异或加密的明文，再与Making-key异或可得到明文，也就是（A异或B异或B=A，csdn对两个^显示有bug），这个在cuckoo哈希中也用到了）
结构体定义：
// 第一部分
typedef struct _ws_ophdr {
unsigned char opcode:4, // 反过来写，转网络字节序
rsv3:1,
rsv2:1,
rsv1:1,
fin:1;
unsigned char pl_len:7,
mask:1;
} ws_ophdr;
// 第二部分
typedef struct _ws_head_126 {
unsigned short payload_length;
char mask_key[4];
} ws_head_126;
typedef struct _ws_head_127 {
long long payload_length;
char mask_key[4];
} ws_head_127;
这里_ws_ophdr反过来写的原因：
比特序 => 小端比特序：比特位从右到左; 网卡比特发送的顺序是按小端比特序发送的，也就是低比特位先发，因此不论发送端是大端还是小端比特序，接收端先接收的也是低比特位。发送端的发送的比特及服务端接收的比特顺序：
位域 => 结构体中，定义顺序从前到后，比特序号从低到高（也就是fin是最高的bit位），因此，根据服务端接收的顺序，_ws_ophdr结构体应该反过来定义。
websocket数据传输
握手成功后，就可以进行数据传输了，服务器解析数据包括两方面：数据长度、密文解密（与mask_key异或）
void umask(char *payload, int length, char *mask_key) {
int i = 0;
for (i = 0;i < length;i ++) {
payload[i] ^= mask_key[i%4]; // 异或
}
}
int transmission(struct ntyevent *ev) {
//ev->buffer; ev->length
ws_ophdr *hdr = (ws_ophdr*)ev->buffer;
printf("length: %d\n", hdr->pl_len);
if (hdr->pl_len < 126) { // 只用第一段
unsigned char *payload = ev->buffer + sizeof(ws_ophdr) + 4; // 6 payload length < 126
if (hdr->mask) { // mask set 1
umask(payload, hdr->pl_len, ev->buffer+2); // 服务器数据解析，与mask_key进行两次异或（A^B^B=A）
}
printf("payload : %s\n", payload);
} else if (hdr->pl_len == 126) {
ws_head_126 *hdr126 = ev->buffer + sizeof(ws_ophdr);
} else {
ws_head_127 *hdr127 = ev->buffer + sizeof(ws_ophdr);
}
}
关闭连接
调用close()函数
WebSocket是很民主的，啥都要协商！建立连接时需要握手协议，连断开连接都需要双方共同完成！其实断开连接直接断开TCP连接就可以了，但是这有点暴力。文明点的方法是发个请求，让对方自己断开。
代码实现
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <openssl/sha.h>
#include <openssl/pem.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
#define BUFFER_LENGTH 4096
#define MAX_EPOLL_EVENTS 1024
#define SERVER_PORT 8888
#define PORT_COUNT 100
#define GUID "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
enum {
WS_HANDSHARK = 0,
WS_TRANMISSION = 1,
WS_END = 2,
};
typedef struct _ws_ophdr {
unsigned char opcode:4, // 反过来写，转网络字节序
rsv3:1,
rsv2:1,
rsv1:1,
fin:1;
unsigned char pl_len:7,
mask:1;
} ws_ophdr;
typedef struct _ws_head_126 {
unsigned short payload_length;
char mask_key[4];
} ws_head_126;
typedef struct _ws_head_127 {
long long payload_length;
char mask_key[4];
} ws_head_127;
typedef int NCALLBACK(int ,int, void*);
struct ntyevent {
int fd;
int events;
void *arg;
int (*callback)(int fd, int events, void *arg);
int status;
char buffer[BUFFER_LENGTH];
int length;
long last_active;
int status_machine;
};
struct eventblock {
struct eventblock *next;
struct ntyevent *events;
};
struct ntyreactor {
int epfd;
int blkcnt;
struct eventblock *evblk; //fd --> 100w
};
int recv_cb(int fd, int events, void *arg);
int send_cb(int fd, int events, void *arg);
struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd);
void nty_event_set(struct ntyevent *ev, int fd, NCALLBACK callback, void *arg) {
ev->fd = fd;
ev->callback = callback;
ev->events = 0;
ev->arg = arg;
ev->last_active = time(NULL);
return ;
}
int nty_event_add(int epfd, int events, struct ntyevent *ev) {
struct epoll_event ep_ev = {0, {0}};
ep_ev.data.ptr = ev;
ep_ev.events = ev->events = events;
int op;
if (ev->status == 1) {
op = EPOLL_CTL_MOD;
} else {
op = EPOLL_CTL_ADD;
ev->status = 1;
}
if (epoll_ctl(epfd, op, ev->fd, &ep_ev) < 0) {
printf("event add failed [fd=%d], events[%d]\n", ev->fd, events);
return -1;
}
return 0;
}
int nty_event_del(int epfd, struct ntyevent *ev) {
struct epoll_event ep_ev = {0, {0}};
if (ev->status != 1) {
return -1;
}
ep_ev.data.ptr = ev;
ev->status = 0;
epoll_ctl(epfd, EPOLL_CTL_DEL, ev->fd, &ep_ev);
return 0;
}
int base64_encode(char *in_str, int in_len, char *out_str) {
BIO *b64, *bio;
BUF_MEM *bptr = NULL;
size_t size = 0;
if (in_str == NULL || out_str == NULL)
return -1;
b64 = BIO_new(BIO_f_base64());
bio = BIO_new(BIO_s_mem());
bio = BIO_push(b64, bio);
BIO_write(bio, in_str, in_len);
BIO_flush(bio);
BIO_get_mem_ptr(bio, &bptr);
memcpy(out_str, bptr->data, bptr->length);
out_str[bptr->length-1] = '\0';
size = bptr->length;
BIO_free_all(bio);
return size;
}
int readline(char *allbuf, int idx, char *linebuf) {
int len = strlen(allbuf);
for(;idx < len;idx ++) {
if (allbuf[idx] == '\r' && allbuf[idx+1] == '\n') {
return idx+2;
} else {
*(linebuf++) = allbuf[idx];
}
}
return -1;
}
// 19 : length of "Sec-WebSocket-Key: "
#define WEBSOCK_KEY_LENGTH 19 // 定义这个宏只是为了注释19的，别人能看懂
int handshark(struct ntyevent *ev) {
char linebuf[1024] = {0};
int idx = 0;
char sec_data[128] = {0};
char sec_accept[32] = {0};
do {
memset(linebuf, 0, 1024);
idx = readline(ev->buffer, idx, linebuf);
if (strstr(linebuf, "Sec-WebSocket-Key")) { // 读WebSocket-Key
//linebuf: Sec-WebSocket-Key: QWz1vB/77j8J8JcT/qtiLQ==
strcat(linebuf, GUID);
SHA1(linebuf + WEBSOCK_KEY_LENGTH, strlen(linebuf + WEBSOCK_KEY_LENGTH), sec_data); // openssl
base64_encode(sec_data, strlen(sec_data), sec_accept);
memset(ev->buffer, 0, BUFFER_LENGTH);
ev->length = sprintf(ev->buffer, "HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n\r\n", sec_accept);
printf("ws response : %s\n", ev->buffer);
break;
}
} while((ev->buffer[idx] != '\r' || ev->buffer[idx+1] != '\n') && idx != -1 );
return 0;
}
void umask(char *payload, int length, char *mask_key) {
int i = 0;
for (i = 0;i < length;i ++) {
payload[i] ^= mask_key[i%4]; // 异或
}
}
int transmission(struct ntyevent *ev) {
//ev->buffer; ev->length
ws_ophdr *hdr = (ws_ophdr*)ev->buffer;
printf("length: %d\n", hdr->pl_len);
if (hdr->pl_len < 126) { // 只用第一段
unsigned char *payload = ev->buffer + sizeof(ws_ophdr) + 4; // 6 payload length < 126
if (hdr->mask) { // mask set 1
umask(payload, hdr->pl_len, ev->buffer+2); // 服务器数据解析，与mask_key进行两次异或（A^B^B=A）
}
printf("payload : %s\n", payload);
} else if (hdr->pl_len == 126) {
ws_head_126 *hdr126 = ev->buffer + sizeof(ws_ophdr);
} else {
ws_head_127 *hdr127 = ev->buffer + sizeof(ws_ophdr);
}
}
int websocket_request(struct ntyevent *ev) {
if (ev->status_machine == WS_HANDSHARK) {
ev->status_machine = WS_TRANMISSION;
handshark(ev);
} else if (ev->status_machine == WS_TRANMISSION) {
transmission(ev);
} else {
}
printf("websocket_request --> %d\n", ev->status_machine);
}
int recv_cb(int fd, int events, void *arg) {
struct ntyreactor *reactor = (struct ntyreactor*)arg;
struct ntyevent *ev = ntyreactor_idx(reactor, fd);
int len = recv(fd, ev->buffer, BUFFER_LENGTH , 0); //
if (len > 0) {
ev->length = len;
ev->buffer[len] = '\0';
printf("C[%d]: machine: %d\n", fd, ev->status_machine);
websocket_request(ev);
nty_event_del(reactor->epfd, ev);
nty_event_set(ev, fd, send_cb, reactor);
nty_event_add(reactor->epfd, EPOLLOUT, ev);
} else if (len == 0) {
nty_event_del(reactor->epfd, ev);
close(ev->fd);
} else {
nty_event_del(reactor->epfd, ev);
close(ev->fd);
printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));
}
return len;
}
int send_cb(int fd, int events, void *arg) {
struct ntyreactor *reactor = (struct ntyreactor*)arg;
struct ntyevent *ev = ntyreactor_idx(reactor, fd);
int len = send(fd, ev->buffer, ev->length, 0);
if (len > 0) {
printf("send[fd=%d], [%d]%s\n", fd, len, ev->buffer);
nty_event_del(reactor->epfd, ev);
nty_event_set(ev, fd, recv_cb, reactor);
nty_event_add(reactor->epfd, EPOLLIN, ev);
} else {
close(ev->fd);
nty_event_del(reactor->epfd, ev);
printf("send[fd=%d] error %s\n", fd, strerror(errno));
}
return len;
}
int accept_cb(int fd, int events, void *arg) {
struct ntyreactor *reactor = (struct ntyreactor*)arg;
if (reactor == NULL) return -1;
struct sockaddr_in client_addr;
socklen_t len = sizeof(client_addr);
int clientfd;
if ((clientfd = accept(fd, (struct sockaddr*)&client_addr, &len)) == -1) {
if (errno != EAGAIN && errno != EINTR) {
}
printf("accept: %s\n", strerror(errno));
return -1;
}
int flag = 0;
if ((flag = fcntl(clientfd, F_SETFL, O_NONBLOCK)) < 0) {
printf("%s: fcntl nonblocking failed, %d\n", __func__, MAX_EPOLL_EVENTS);
return -1;
}
struct ntyevent *event = ntyreactor_idx(reactor, clientfd);
event->status_machine = WS_HANDSHARK;
nty_event_set(event, clientfd, recv_cb, reactor);
nty_event_add(reactor->epfd, EPOLLIN, event);
printf("new connect [%s:%d], pos[%d]\n",
inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), clientfd);
return 0;
}
int init_sock(short port) {
int fd = socket(AF_INET, SOCK_STREAM, 0);
fcntl(fd, F_SETFL, O_NONBLOCK);
struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_port = htons(port);
bind(fd, (struct sockaddr*)&server_addr, sizeof(server_addr));
if (listen(fd, 20) < 0) {
printf("listen failed : %s\n", strerror(errno));
}
return fd;
}
int ntyreactor_alloc(struct ntyreactor *reactor) {
if (reactor == NULL) return -1;
if (reactor->evblk == NULL) return -1;
struct eventblock *blk = reactor->evblk;
while (blk->next != NULL) {
blk = blk->next;
}
struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
if (evs == NULL) {
printf("ntyreactor_alloc ntyevents failed\n");
return -2;
}
memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));
if (block == NULL) {
printf("ntyreactor_alloc eventblock failed\n");
return -2;
}
memset(block, 0, sizeof(struct eventblock));
block->events = evs;
block->next = NULL;
blk->next = block;
reactor->blkcnt ++;
return 0;
}
struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd) {
int blkidx = sockfd / MAX_EPOLL_EVENTS;
while (blkidx >= reactor->blkcnt) {
ntyreactor_alloc(reactor);
}
int i = 0;
struct eventblock *blk = reactor->evblk;
while(i ++ < blkidx && blk != NULL) {
blk = blk->next;
}
return &blk->events[sockfd % MAX_EPOLL_EVENTS];
}
int ntyreactor_init(struct ntyreactor *reactor) {
if (reactor == NULL) return -1;
memset(reactor, 0, sizeof(struct ntyreactor));
reactor->epfd = epoll_create(1);
if (reactor->epfd <= 0) {
printf("create epfd in %s err %s\n", __func__, strerror(errno));
return -2;
}
struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
if (evs == NULL) {
printf("ntyreactor_alloc ntyevents failed\n");
return -2;
}
memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));
if (block == NULL) {
printf("ntyreactor_alloc eventblock failed\n");
return -2;
}
memset(block, 0, sizeof(struct eventblock));
block->events = evs;
block->next = NULL;
reactor->evblk = block;
reactor->blkcnt = 1;
return 0;
}
int ntyreactor_destory(struct ntyreactor *reactor) {
close(reactor->epfd);
//free(reactor->events);
struct eventblock *blk = reactor->evblk;
struct eventblock *blk_next = NULL;
while (blk != NULL) {
blk_next = blk->next;
free(blk->events);
free(blk);
blk = blk_next;
}
return 0;
}
int ntyreactor_addlistener(struct ntyreactor *reactor, int sockfd, NCALLBACK *acceptor) {
if (reactor == NULL) return -1;
if (reactor->evblk == NULL) return -1;
//reactor->evblk->events[sockfd];
struct ntyevent *event = ntyreactor_idx(reactor, sockfd);
nty_event_set(event, sockfd, acceptor, reactor);
nty_event_add(reactor->epfd, EPOLLIN, event);
return 0;
}
int ntyreactor_run(struct ntyreactor *reactor) {
if (reactor == NULL) return -1;
if (reactor->epfd < 0) return -1;
if (reactor->evblk == NULL) return -1;
struct epoll_event events[MAX_EPOLL_EVENTS+1];
int checkpos = 0, i;
while (1) {
int nready = epoll_wait(reactor->epfd, events, MAX_EPOLL_EVENTS, 1000);
if (nready < 0) {
printf("epoll_wait error, exit\n");
continue;
}
for (i = 0;i < nready;i ++) {
struct ntyevent *ev = (struct ntyevent*)events[i].data.ptr;
if ((events[i].events & EPOLLIN) && (ev->events & EPOLLIN)) {
ev->callback(ev->fd, events[i].events, ev->arg);
}
if ((events[i].events & EPOLLOUT) && (ev->events & EPOLLOUT)) {
ev->callback(ev->fd, events[i].events, ev->arg);
}
}
}
}
// <remoteip, remoteport, localip, localport>
int main(int argc, char *argv[]) {
unsigned short port = SERVER_PORT; // listen 8888
if (argc == 2) {
port = atoi(argv[1]);
}
struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));
ntyreactor_init(reactor);
int i = 0;
int sockfds[PORT_COUNT] = {0};
for (i = 0;i < PORT_COUNT;i ++) {
sockfds[i] = init_sock(port+i);
ntyreactor_addlistener(reactor, sockfds[i], accept_cb);
}
ntyreactor_run(reactor);
ntyreactor_destory(reactor);
for (i = 0;i < PORT_COUNT;i ++) {
close(sockfds[i]);
}
free(reactor);
return 0;
}
![[ 数据结构 ] 堆排序--------思路、图解、代码](https://img-blog.csdnimg.cn/img_convert/14005edc5bb9dc64e31b161bb144ead7.png)
