websocket
一、什么是websocket
- WebSocket是HTML5下一种新的协议(websocket协议本质上是一个基于tcp的协议);
- 它实现了浏览器与服务器全双工通信,能更好的节省服务器资源和带宽并达到实时通讯的目的;
- Websocket是一个持久化的协议。
二、websocket的原理
- websocket约定了一个通信的规范,通过一个握手的机制,客户端和服务器之间能建立一个类似tcp的连接,从而方便它们之间的通信;
- 在websocket出现之前,web交互一般是基于http协议的短连接或者长连接;
- websocket是一种全新的协议,不属于http无状态协议,协议名为"ws"。
三、websocket与http的关系
相同点:
- 都是基于tcp的,都是可靠性传输协议
- 都是应用层协议
不同点:
- WebSocket是双向通信协议,模拟Socket协议,可以双向发送或接受信息
- HTTP是单向的
- WebSocket是需要浏览器和服务器握手进行建立连接的
- 而http是浏览器发起向服务器的连接,服务器预先并不知道这个连接
联系:
- WebSocket在建立握手时,数据是通过HTTP传输的。但是建立之后,在真正传输时候是不需要HTTP协议的
总结(总体过程):
- 首先,客户端发起http请求,经过3次握手后,建立起TCP连接;http请求里存放WebSocket支持的版本号等信息,如:Upgrade、Connection、WebSocket-Version等;
- 然后,服务器收到客户端的握手请求后,同样采用HTTP协议回馈数据;
- 最后,客户端收到连接成功的消息后,开始借助于TCP传输信道进行全双工通信。
四、websocket解决的问题
1.http存在的问题
- http是一种无状态协议,每当一次会话完成后,服务端都不知道下一次的客户端是谁,需要每次知道对方是谁,才进行相应的响应,因此本身对于实时通讯就是一种极大的障碍;
- http协议采用一次请求,一次响应,每次请求和响应就携带有大量的header头,对于实时通讯来说,解析请求头也是需要一定的时间,因此,效率也更低下;
- 最重要的是,需要客户端主动发,服务端被动发,也就是一次请求,一次响应,不能实现主动发送。
2.long poll(长轮询)
- 对于以上情况就出现了http解决的第一个方法——长轮询;
- 基于http的特性,简单点说,就是客户端发起长轮询,如果服务端的数据没有发生变更,会 hold 住请求,直到服务端的数据发生变化,或者等待一定时间超时才会返回。返回后,客户端又会立即再次发起下一次长轮询;
- 优点是解决了http不能实时更新的弊端,因为这个时间很短,发起请求即处理请求返回响应,实现了“伪·长连接”;
- 张三取快递的例子,张三今天一定要取到快递,他就一直站在快递点,等待快递一到,立马取走。
从例子上来看有个问题:
- 假如有好多人一起在快递站等快递,那么这个地方是否足够大,(抽象解释:需要有很高的并发,同时有很多请求等待在这里)
总的来看:
- 推送延迟。服务端数据发生变更后,长轮询结束,立刻返回响应给客户端。
- 服务端压力。长轮询的间隔期一般很长,例如 30s、60s,并且服务端 hold 住连接不会消耗太多服务端资源。
3.Ajax轮询
- 基于http的特性,简单点说,就是规定每隔一段时间就由客户端发起一次请求,查询有没有新消息,如果有,就返回,如果没有等待相同的时间间隔再次询问;
- 优点是解决了http不能实时更新的弊端,因为这个时间很短,发起请求即处理请求返回响应,把这个过程放大n倍,本质上还是request = response;
- 举个形象的例子(假设张三今天有个快递快到了,但是张三忍耐不住,就每隔十分钟给快递员或者快递站打电话,询问快递到了没,每次快递员就说还没到,等到下午张三的快递到了,but,快递员不知道哪个电话是张三的,(可不是只有张三打电话,还有李四,王五),所以只能等张三打电话,才能通知他,你的快递到了)。
从例子上来看有两个问题:
假如说,张三打电话的时间间隔为10分钟,当他收到快递前最后一次打电话,快递员说没到,他刚挂掉电话,快递入库了(就是到了),那么等下一次时间到了,张三打电话知道快递到了,那么这样的通讯算不算实时通讯?很显然,不算,中间有十分钟的时间差,还不算给快递员打电话的等待时间(抽象的解释:每次request的请求时间间隔等同于十分钟,请求解析相当于等待)
假如说张三所在的小区每天要收很多快递,每个人都采取主动给快递员打电话的方式,那么快递员需要以多快的速度接到,其他人打电话占线也是问题(抽象解释:请求过多,服务端响应也会变慢)。
总的来看,Ajax轮询存在的问题:
-
推送延迟。
-
服务端压力。配置一般不会发生变化,频繁的轮询会给服务端造成很大的压力。
-
推送延迟和服务端压力无法中和。降低轮询的间隔,延迟降低,压力增加;增加轮询的间隔,压力降低,延迟增高
4.websocket的改进
一旦WebSocket连接建立后,后续数据都以帧序列的形式传输。在客户端断开WebSocket连接或Server端中断连接前,不需要客户端和服务端重新发起连接请求。在海量并发及客户端与服务器交互负载流量大的情况下,极大的节省了网络带宽资源的消耗,有明显的性能优势,且客户端发送和接受消息是在同一个持久连接上发起,实现了“真·长链接”,实时性优势明显。
WebSocket有以下特点:
- 是真正的全双工方式,建立连接后客户端与服务器端是完全平等的,可以互相主动请求。而HTTP长连接基于HTTP,是传统的客户端对服务器发起请求的模式。
- HTTP长连接中,每次数据交换除了真正的数据部分外,服务器和客户端还要大量交换HTTP header,信息交换效率很低。Websocket协议通过第一个request建立了TCP连接之后,之后交换的数据都不需要发送 HTTP header就能交换数据,这显然和原有的HTTP协议有区别所以它需要对服务器和客户端都进行升级才能实现(主流浏览器都已支持HTML5)
什么时候用到websocket?
1.即时通讯:login,register,添加好友,消息转发
2.直播
自定义协议由两部分组成:1.tcp包本身的信息,2.业务协议,加版本号
websocket主要包括以下内容:
1.websocket协议格式?
2.websocket如何验证客户端合法?
3.明文与密文如何传输?
4.websocket如何断开?
1.websocket请求连接发送的包符合http格式,handshark。有几个字段http没有,connection,upgrade。
#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, 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; } /* ev->buffer : ev->length 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 str = "QWz1vB/77j8J8JcT/qtiLQ==258EAFA5-E914-47DA-95CA-C5AB0DC85B11" sha = SHA1(str); value = base64_encode(sha); */ // 19 : length of "Sec-WebSocket-Key: " #define WEBSOCK_KEY_LENGTH 19 int handshark(struct ntyevent *ev) { //ev->buffer , ev->length 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")) { //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; } void umask(char *payload, int length, char *mask_key) { int i = 0; for (i = 0;i < length;i ++) { payload[i] ^= mask_key[i%4]; } } 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) { // 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); } 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); //printf("[fd=%d] pos[%ld], closed\n", fd, ev-reactor->events); } 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) { /* long now = time(NULL); for (i = 0;i < 100;i ++, checkpos ++) { if (checkpos == MAX_EPOLL_EVENTS) { checkpos = 0; } if (reactor->events[checkpos].status != 1) { continue; } long duration = now - reactor->events[checkpos].last_active; if (duration >= 60) { close(reactor->events[checkpos].fd); printf("[fd=%d] timeout\n", reactor->events[checkpos].fd); nty_event_del(reactor->epfd, &reactor->events[checkpos]); } } */ 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); } } } } // 3, 6w, 1, 100 == // <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; }
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原文链接:https://blog.csdn.net/qq_54773998/article/details/123863493