nginx websocket有什么特点

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websocket协议简介

websocket是基于TCP的应用层协议，用于在C/S架构的应用中实现双向通信，rfc文档说明rfc6455。
websocket在建立连接时会使用HTTP协议，所以websocket协议是基于HTTP协议实现的。

目前很多卡牌类的游戏选择使用websocket协议进行通信。

websocket具备如下特点：

1.可以进行双向通信，会话通信实时性强。

2.建立起websocket连接，可以一直保持连接，在此期间可以源源不断的发送消息，直到关闭请求。避免了HTTP的非状态性(连接时总开销减少)。和http相比连接创建后，客户端服务端进行数据交换时，协议控制的数据包头部较小(通信量减少)。

3.web服务器与客户端之间建立起连接后，所有的通信都依靠这个专用协议进行。通信过程中可互相发送JSON、XML、HTML或图片等任意格式的数据。不论服务器还是客户端，任意一方都可直接向对方发送数据。

4.更好的二进制支持，支持扩展。

websocket协议格式：

0                   1                   2                   3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1+-+-+-+-+-------+-+-------------+-------------------------------+|F|R|R|R| opcode|M| Payload len |    Extended payload length    ||I|S|S|S|  (4)  |A|     (7)     |             (16/64)           ||N|V|V|V|       |S|             |   (if payload len==126/127)   || |1|2|3|       |K|             |                               |+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +|     Extended payload length continued, if payload len == 127  |+ - - - - - - - - - - - - - - - +-------------------------------+|                               |Masking-key, if MASK set to 1  |+-------------------------------+-------------------------------+| Masking-key (continued)       |          Payload Data         |+-------------------------------- - - - - - - - - - - - - - - - +:                     Payload Data continued ...                :+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +|                     Payload Data continued ...                |+---------------------------------------------------------------+

nginx支持websocket说明

在使用nginx开启websocket配置时，可以通过在server{}块中配置websocket配置。

server {      listen   80;      server_name www.domain.com;      location / {         proxy_pass   http://127.0.0.1:8080/; //回源地址 　　　　proxy_http_version 1.1;         proxy_read_timeout   600s; //超时设置         //启用支持websocket         proxy_set_header Upgrade $http_upgrade;         proxy_set_header Connection "upgrade";      }}

如上配置它表明websocket请求连接的时候，升级连接将http连接变成websocket连接。

但这里会有一个问题，这样在server{}块中配置websocket，该server{}必须处理websocket流量，所有发往后端的流量都带上upgrade和connection头。

proxy_set_header Upgrade $http_upgrade;

proxy_set_header Connection $connection_upgrade;

nginx websocket源码优化

在server{}中配置websocket时，所有发往后端upstream的流量会添加websocket头。

假如发往后端upstream的请求，有的需要添加websocket头升级为websocket，有的请求不需要，如果继续使用原生的nginx配置，会导致该场景该配置，出现问题。

所以该场景下需改动和优化nginx源码，来区分client的流量是否是websocket。

ngx_http_proxy_websocket_headers：区别在于connection和upgrade

static ngx_keyval_t  ngx_http_proxy_websocket_headers[] = {{ ngx_string("Host"), ngx_string("$proxy_host") },{ ngx_string("Connection"), ngx_string("Upgrade") },{ ngx_string("Content-Length"), ngx_string("$proxy_internal_body_length") },{ ngx_string("Transfer-Encoding"), ngx_string("$proxy_internal_chunked") },{ ngx_string("TE"), ngx_string("") },{ ngx_string("Keep-Alive"), ngx_string("") },{ ngx_string("Expect"), ngx_string("") },{ ngx_string("Upgrade"), ngx_string("websocket") },{ ngx_null_string, ngx_null_string }};#ifdef NGX_WEBSOCKET_INNER// 通过headers来initrc = ngx_http_proxy_init_headers(cf, conf, &conf->websocket_headers,ngx_http_proxy_websocket_headers);if (rc != NGX_OK) {return NGX_CONF_ERROR;}#endifstatic ngx_int_tngx_http_process_connection(ngx_http_request_t *r, ngx_table_elt_t *h,ngx_uint_t offset){...// 获取upgrade标志if (ngx_strcasestrn(h->value.data, "Upgrade", 7 - 1)) {r->is_websocket_request |= NGX_WEBSOCKET_HEADER_CONNECTION;}...}if (r->headers_in.upgrade == NULL) {goto not_websocket_request;} else if ((r->is_websocket_request & NGX_WEBSOCKET_HEADER_CONNECTION) == 0) {goto not_websocket_request;// } else if (ngx_strncasecmp(r->headers_in.upgrade->value.data, (u_char *)"websocket", 9) == 0) {// 判断是否含有websocket，添加标志} else if (ngx_strcasestrn(r->headers_in.upgrade->value.data, "websocket", 9 - 1)) {r->is_websocket_request |= NGX_WEBSOCKET_HEADER_UPGRADE;}// 两种标志都有，r->websocket_request 标志位置位if (r->is_websocket_request == (NGX_WEBSOCKET_HEADER_UPGRADE | NGX_WEBSOCKET_HEADER_CONNECTION)) {r->websocket_request = 1;r->http_version = NGX_HTTP_VERSION_11;} else {r->websocket_request = 0;}ngx_http_proxy_process_header配置upstream的标志位static ngx_int_tngx_http_proxy_process_header(ngx_http_request_t *r){...if (u->headers_in.status_n == NGX_HTTP_SWITCHING_PROTOCOLS) {u->keepalive = 0;if (r->headers_in.upgrade) {u->upgrade = 1;}}...}在ngx_http_upstream_send_response种使用该标志位static voidngx_http_upstream_send_response(ngx_http_request_t *r, ngx_http_upstream_t *u){...if (u->upgrade) {ngx_http_upstream_upgrade(r, u);return;}...}ngx_http_upstream_upgrade给上下游设置读写事件static voidngx_http_upstream_upgrade(ngx_http_request_t *r, ngx_http_upstream_t *u){...u->read_event_handler = ngx_http_upstream_upgraded_read_upstream;u->write_event_handler = ngx_http_upstream_upgraded_write_upstream;r->read_event_handler = ngx_http_upstream_upgraded_read_downstream;r->write_event_handler = ngx_http_upstream_upgraded_write_downstream;...}每个读写时间所用的函数都是一样的，入参不同:from_upstream代表是否是后端，do_write代表是否是写事件下面以upstream的读事件为例static voidngx_http_upstream_process_upgraded(ngx_http_request_t *r,ngx_uint_t from_upstream, ngx_uint_t do_write){...// from_upstream为1，src为upstream（上游），dst为downstream（下游）if (from_upstream) {src = upstream;dst = downstream;b = &u->buffer;}for ( ;; ) {// do_write为0忽略。if (do_write) {}if (size && src->read->ready) {// src为upstream，用来读n = src->recv(src, b->last, size);// n >0 接收大于0的字节数，do_write置为1，continue进行写入if (n > 0) {do_write = 1;b->last += n;if (from_upstream) {u->state->bytes_received += n;}continue;}// 加入三个计时器，upstream读写都加，downstream只加写入，相当于除了client的接收没加计时器，都加了if (upstream->write->active && !upstream->write->ready) {ngx_add_timer(upstream->write, u->conf->send_timeout);} else if (upstream->write->timer_set) {ngx_del_timer(upstream->write);}if (upstream->read->active && !upstream->read->ready) {ngx_add_timer(upstream->read, u->conf->read_timeout);} else if (upstream->read->timer_set) {ngx_del_timer(upstream->read);}if (downstream->write->active && !downstream->write->ready) {ngx_add_timer(downstream->write, clcf->send_timeout);} else if (downstream->write->timer_set) {ngx_del_timer(downstream->write);}...}

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