1.什么是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）
websocket使得客户端和服务器之间的数据交换变得更加简单，允许服务端主动向客户端推送数据。在WebSocket API中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输。
2.总体过程：
2.1 握手过程：
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。
第一个一条信息来自|Sec-WebSocket-Key|报头字段在客户端握手中:Sec-WebSocket-Key: fmXyv9eR4PG9L53s09jQLA==对于这个报头字段，服务器必须接受该值(作为当前值)在报头字段中，例如，base64编码的[RFC4648]版本减任何前导和尾随空格)，并将其与全局唯一标识符(GUID， [RFC4122])“258 eafa5-e914-47da -95CA-C5AB0DC85B11”的字符串形式，不太可能被使用网络端点不理解WebSocket协议。一个SHA-1哈希(160位)[FIPS;180-3]，base64编码，然后返回到服务器的握手。
###websocket 浏览器-->服务器
GET / HTTP/1.1
Host: 192.168.240.128:8888
Connection: Upgrade ##升级版
Pragma: no-cache
Cache-Control: no-cache
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36 Core/1.94.172.400 QQBrowser/11.1.5140.400
Upgrade: websocket #websockrt
Origin: null
Sec-WebSocket-Version: 13
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Sec-WebSocket-Key: fmXyv9eR4PG9L53s09jQLA==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
###握手信息拼接Key+GUID
Key = fmXyv9eR4PG9L53s09jQLA==
GUID = 258EAFA5-E914-47DA-95CA-C5AB0DC85B11
str = Key+GUID = fmXyv9eR4PG9L53s09jQLA==258EAFA5-E914-47DA-95CA-C5AB0DC85B11
###哈希SHA-1
sha = SHA-1(str)
###base64转换
vaule = base64-encoded(sha);
###服务器-->浏览器
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: vaule具体代码实现
//响应包拼接
int ws_handshark(struct ntyevent *ev)
{
int idx = 0;
char sec_data[128] = {0};
char sec_accept[128] = {0};
do{
char linebuff[1024] = {0};
idx = readline(ev->buffer, idx, linebuff);
if(strstr(linebuff, "Sec-WebSocket-Key") > 0){
//Sec-WebSocket-Key: hGI6OP19pWseAnpMcEnb2g==
//Key+GUID
//Sec-WebSocket-Key: hGI6OP19pWseAnpMcEnb2g==258EAFA5-E914-47DA-95CA-C5AB0DC85B11
strcat(linebuff, GUID);
//哈希SHA-1
SHA1(linebuff + strlen("Sec-WebSocket-Key: "), strlen(linebuff + strlen("Sec-WebSocket-Key: ")), sec_data);
//base64 编码
base64_encode(sec_data, strlen(sec_data), sec_accept);
//printf("idx: %d, line: %ld\n",idx, sizeof("Sec-WebSocket-Key: "));
//printf("idx: %d, line: %ld\n",idx, strlen("Sec-WebSocket-Key: "));
printf("idx %d ; line:%s\n", idx, sec_accept);
memcpy(ev->sec_accept, sec_accept, ACCEPT_KEY_LENGTH);
}
//printf("line %d ; line:%s\n", idx, linebuff);
}while((ev->buffer[idx] != '\r' || ev->buffer[idx + 1] != '\n') && idx != -1); //两组\r\n结束
return 0;
}
//应答 #服务器-->浏览器
int ws_response(struct ntyevent* ev)
{
ev->wlength = sprintf(ev->wbuffer, "HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n\r\n", ev->sec_accept);
printf("response: %s\n", ev->wbuffer);
return ev->wlength;
}相关视频推荐
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2.2 接收和发送
websocket协议的数据帧
FIN :1bit
指示这是消息中的最后一个片段。第一个碎片也可能是最后的碎片。
RSV1、RSV2、RSV3:各1bit
必须为0，除非协商一个定义含义的扩展为非零值。如果接收到一个非零值，并且没有
协商好的扩展定义了这种非零的含义值，接收端点必须失败WebSocketConnection.
Opcode: 4 bits
定义“有效负载数据”的解释。如果一个未知的操作码，接收端点必须失败WebSocket Connection_。定义了以下值。
* %x0 表示延续帧
* %x1 表示文本框架
* %x2 表示二进制帧
* %x3-7 为其他非控制帧保留
* %x8 表示连接关闭
* %x9 表示ping
* %xA 表示pong
* %xB-F 为进一步的控制帧保留
Mask: 1 bit
定义是否屏蔽“有效负载数据”。如果设置为1，则a屏蔽键包含在屏蔽键中，用于解除屏蔽。
解除屏蔽
j = i MOD 4
transformed-octet-i = original-octet-i XOR masking-key-octet-j
Payload length: 7 bits, 7+16 bits, or 7+64 bits
“有效载荷数据”的长度，以字节为单位:如果0-125，则为有效载荷长度。如果126，下面的2个字节被解释为a16位无符号整数是有效载荷长度。如果127,后面的8个字节被解释为64位无符号整数最有效位必须为0)为有效载荷长度。多字节长度量用网络字节顺序表示。请注意,在所有情况下，必须使用最小字节数进行编码长度。
将数据帧映射到结构体，小端字节序
struct ws_ophdr { //小端
unsigned char opcode:4,
rsv3:1,
rsv2:1,
rsv1:1,
fin:1;
unsigned char pl_len:7,
mask:1;
};具体代码
//Masking-key, if MASK set to 1 解除数据屏蔽
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 ws_tranmission(struct ntyevent *ev)
{
struct ws_ophdr *hdr = (struct ws_ophdr *)ev->buffer;
if (hdr->pl_len < 126) {
unsigned char *payload = NULL;
if (hdr->mask) {
payload = ev->buffer + 6;
umask(payload, hdr->pl_len, ev->buffer + 2);
} else {
payload = ev->buffer + 2;
}
printf("payload: %s\n", payload);
} else if (hdr->pl_len == 126) {
} else if (hdr->pl_len == 127) {
} else {
//assert(0);
}
return 0;
}3. 完整代码
//gcc reactor_server_websocket.c -o server -lssl -lcrypto
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define GUID "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
//状态机
enum {
WS_HANDSHARK = 0, //握手状态
WS_TRANMISSION = 1, //数据传输
WS_END = 2, //终止传输
WS_COUNT
};
struct ws_ophdr { //小端
unsigned char opcode:4,
rsv3:1,
rsv2:1,
rsv1:1,
fin:1;
unsigned char pl_len:7,
mask:1;
};
#define BUFFER_LENGTH 1024
#define ACCEPT_KEY_LENGTH 64
#define MAX_EPOLL_EVENTS 1024 //epoll事件数量
#define SERVER_PORT 8888
#define PORT_COUNT 1
typedef int NCALLBACK(int ,int ,void*);
//管理每一个io fd的结构体
struct ntyevent{
int fd; //io fd
int events;
void *arg;
int (*callback)(int fd, int events, void* arg); //执行回调函数
int status; //判断是否已有事件
char buffer[BUFFER_LENGTH]; //用户缓冲区 //request
int length; //用户缓冲区长度
char wbuffer[BUFFER_LENGTH]; //response
int wlength;
char sec_accept[ACCEPT_KEY_LENGTH];
int wsstatus; //0, 1, 2, 3 描述状态机
};
//管理ntyevent fd的块
struct eventblock{
struct eventblock* next; //指向ntyevent fd集合
struct ntyevent* events; //指向下一个ntyevent fd的块
};
//reacotr结点
struct ntyreactor{
int epfd; //epoll fd
int blkcnt; //ntyevent fd的块 计数
struct eventblock* evblks; //指向ntyevent fd的块头结点
};
int recv_cb(int fd, int events, void *arg);
int send_cb(int fd, int events, void *arg);
int accept_cb(int fd, int events, void* arg);
struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd);
//io fd结构体设置
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;
return ;
}
//io fd add
int nty_event_add(int epfd, int events, struct ntyevent *ev)
{
struct epoll_event ep_ev = {0, {0}};
ep_ev.data.ptr = ev; //io fd结构体
ep_ev.events = ev->events = events; //需要检测的fd事件
int op; //操作类型
if(ev->status == 1){
op = EPOLL_CTL_MOD; //修改
}else{
op = EPOLL_CTL_ADD; //添加
ev->status = 1; //标志已经添加
}
if(epoll_ctl(epfd, op, ev->fd, &ep_ev) <0 ){ //绑定
printf("event add failed [fd=%d], events[%d]\n", ev->fd, events);
return -1;
}
return 0;
}
//io fd del
int nty_event_del(int epfd, struct ntyevent* ev)
{
struct epoll_event ep_ev = {0, {0}};
if(ev->status != 1){ //没有添加过检测的fd事件
return -1;
}
ep_ev.data.ptr = ev;
ev->status = 0; //标志未添加
epoll_ctl(epfd, EPOLL_CTL_DEL, ev->fd, &ep_ev);
return 0;
}
//读行
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;
}
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;
}
//握手流程
int ws_handshark(struct ntyevent *ev)
{
int idx = 0;
char sec_data[128] = {0};
char sec_accept[128] = {0};
do{
char linebuff[1024] = {0};
idx = readline(ev->buffer, idx, linebuff);
if(strstr(linebuff, "Sec-WebSocket-Key") > 0){
//Sec-WebSocket-Key: hGI6OP19pWseAnpMcEnb2g==
//Key+GUID
//Sec-WebSocket-Key: hGI6OP19pWseAnpMcEnb2g==258EAFA5-E914-47DA-95CA-C5AB0DC85B11
strcat(linebuff, GUID);
//哈希SHA-1
SHA1(linebuff + strlen("Sec-WebSocket-Key: "), strlen(linebuff + strlen("Sec-WebSocket-Key: ")), sec_data);
//base64 编码
base64_encode(sec_data, strlen(sec_data), sec_accept);
//printf("idx: %d, line: %ld\n",idx, sizeof("Sec-WebSocket-Key: "));
//printf("idx: %d, line: %ld\n",idx, strlen("Sec-WebSocket-Key: "));
printf("idx %d ; line:%s\n", idx, sec_accept);
memcpy(ev->sec_accept, sec_accept, ACCEPT_KEY_LENGTH);
}
//printf("line %d ; line:%s\n", idx, linebuff);
}while((ev->buffer[idx] != '\r' || ev->buffer[idx + 1] != '\n') && idx != -1); //两组\r\n结束
return 0;
}
//Masking-key, if MASK set to 1 解除数据屏蔽
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 ws_tranmission(struct ntyevent *ev)
{
struct ws_ophdr *hdr = (struct ws_ophdr *)ev->buffer;
if (hdr->pl_len < 126) {
unsigned char *payload = NULL;
if (hdr->mask) {
payload = ev->buffer + 6;
umask(payload, hdr->pl_len, ev->buffer + 2);
} else {
payload = ev->buffer + 2;
}
printf("payload: %s\n", payload);
} else if (hdr->pl_len == 126) {
} else if (hdr->pl_len == 127) {
} else {
//assert(0);
}
return 0;
}
//请求 协议解析
int ws_request(struct ntyevent * ev)
{
if (ev->wsstatus == WS_HANDSHARK) {
ws_handshark(ev);
ev->wsstatus = WS_TRANMISSION; //状态改变
} else if (ev->wsstatus == WS_TRANMISSION) {
ws_tranmission(ev);
}
}
//应答 #服务器-->浏览器
int ws_response(struct ntyevent* ev)
{
ev->wlength = sprintf(ev->wbuffer, "HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n\r\n", ev->sec_accept);
printf("response: %s\n", ev->wbuffer);
return ev->wlength;
}
//recv回调
int recv_cb(int fd, int events, void* arg)
{
struct ntyreactor* reactor = (struct ntyreactor*)arg;
struct ntyevent* ev = ntyreactor_idx(reactor, fd);
if(ev == NULL)return -1;
int len = recv(fd, ev->buffer, BUFFER_LENGTH, 0);
nty_event_del(reactor->epfd, ev);
if (len > 0) {
ev->length = len;
ev->buffer[len] = '\0';
//printf("recv [%d]:%s\n", fd, ev->buffer);
ws_request(ev);
//将fd 设置为发送事件
nty_event_set(ev, fd, send_cb, reactor);
nty_event_add(reactor->epfd, EPOLLOUT, ev);
} else if (len == 0) { //客户端断开连接
nty_event_del(reactor->epfd, ev);
printf("recv_cb --> disconnect\n");
close(ev->fd);
} else { //返回错误
if (errno == EAGAIN && errno == EWOULDBLOCK) { //
} else if (errno == ECONNRESET){
nty_event_del(reactor->epfd, ev);
close(ev->fd);
}
printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));
}
return len;
}
//send回调
int send_cb(int fd, int events, void* arg)
{
struct ntyreactor* reactor = (struct ntyreactor*)arg;
struct ntyevent* ev = ntyreactor_idx(reactor, fd);
if (ev == NULL) return -1;
ws_response(ev);
int len = send(fd, ev->wbuffer, ev->length, 0);
if (len > 0) {
printf("send[fd=%d], [%d]%s\n", fd, len, ev->wbuffer);
//发送后，将fd设置为接收事件
nty_event_del(reactor->epfd, ev);
nty_event_set(ev, fd, recv_cb, reactor);
nty_event_add(reactor->epfd, EPOLLIN, ev);
} else { //发送失败
nty_event_del(reactor->epfd, ev);
close(ev->fd);
printf("send[fd=%d] error %s\n", fd, strerror(errno));
}
return len;
}
//客户端接入回调
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;
//客户端接入
if ((clientfd = accept(fd, (struct sockaddr*)&client_addr, &len)) == -1) {
if (errno != EAGAIN && errno != EINTR) {
}
printf("accept: %s\n", strerror(errno));
return -1;
}
//设置非阻塞fd
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);
if (event == NULL) return -1;
//将该fd设置为recv
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;
}
//创建socket监听
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 -1;
}
printf("listen server port : %d\n", port);
return fd;
}
//reactor扩展大小
int ntyreactor_alloc(struct ntyreactor* reactor)
{
if(reactor == NULL) return -1;
if(reactor->evblks == NULL) return -1;
struct eventblock* blk = reactor->evblks; //块的头结点
//找尾节点
while(blk->next != NULL){ //找到尾节点
blk = blk->next;
}
struct ntyevent* evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
if (evs == NULL) {
printf("ntyreactor_alloc ntyevent failed\n");
return -2;
}
memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
struct eventblock *block = malloc(sizeof(struct eventblock));
if (block == NULL) {
printf("ntyreactor_alloc eventblock failed\n");
return -3;
}
//io fd集合连接成块
block->events = evs;
block->next = NULL;
//指向新块
blk->next = block;
reactor->blkcnt ++;
return 0;
}
//根据io fd来找fd结构体
struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd) {
if (reactor == NULL) return NULL;
if (reactor->evblks == NULL) return NULL;
int blkidx = sockfd / MAX_EPOLL_EVENTS; //在哪一个块
while (blkidx >= reactor->blkcnt) { //大小不够扩容
ntyreactor_alloc(reactor);
}
int i = 0;
struct eventblock *blk = reactor->evblks; //头结点块
while (i++ != blkidx && blk != NULL) { //找到所在的块
blk = blk->next;
}
return &blk->events[sockfd % MAX_EPOLL_EVENTS]; //返回fd结构体
}
//reactor初始化
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;
}
//创建第一个块
struct ntyevent* evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
if (evs == NULL) {
printf("create epfd in %s err %s\n", __func__, strerror(errno));
close(reactor->epfd);
return -3;
}
memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
struct eventblock *block = malloc(sizeof(struct eventblock));
if (block == NULL) {
free(evs);
close(reactor->epfd);
return -3;
}
block->events = evs;
block->next = NULL;
reactor->evblks = block;
reactor->blkcnt = 1;
return 0;
}
//销毁reactor
int ntyreactor_destory(struct ntyreactor* reactor)
{
close(reactor->epfd);
struct eventblock *blk = reactor->evblks;
struct eventblock *blk_next;
while (blk != NULL) {
blk_next = blk->next;
free(blk->events);
free(blk);
blk = blk_next;
}
return 0;
}
//初始化接收连接socket
int ntyreactor_addlistener(struct ntyreactor* reactor, int sockfd, NCALLBACK *acceptor){
if (reactor == NULL) return -1;
if (reactor->evblks == NULL) return -1;
struct ntyevent* event = ntyreactor_idx(reactor, sockfd);
if (event == NULL) return -1;
nty_event_set(event, sockfd, acceptor, reactor);
nty_event_add(reactor->epfd, EPOLLIN, event);
return 0;
}
//reactor事件循环
int ntyreactor_run(struct ntyreactor* reactor)
{
if (reactor == NULL) return -1;
if (reactor->epfd < 0) return -1;
if (reactor->evblks == 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; //发生事件的io fd结构体
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);
}
}
}
}
int main(int argc, char *argv[]) {
struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));
ntyreactor_init(reactor);
//起始的端口号
unsigned short port = SERVER_PORT;
if (argc == 2) {
port = atoi(argv[1]);
}
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;
} 4.运行结果
总结：
1. websocket是全双工方式，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。
2. 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。
