该项目的目标是有一个JVM（静态编程语言）服务器和一个Python客户端通过websocket相互通信。服务器必须向客户端发送更新，客户端将处理这些更新。

服务器是一个Spring Boot应用程序，运行Spring Boot websocket服务器。客户端目前只是一个Python脚本，运行websocket客户端连接到服务器。

什么是工作：

• 列表项
• 客户端可以连接到服务器
• 客户端可以连接到服务器上的主题（使用STOMP）
• 客户端可以向服务器发送消息，服务器接收并处理此消息
• 服务器可以在websocket上发送消息

什么不起作用：

• 客户端没有收到来自服务器的消息

我已经尝试了客户端的接收部分，通过连接到websocket.org（ws://echo.websocket.org）的回显服务器，客户端从服务器接收回显消息。所以在我看来，问题不在客户端。

静态编程语言服务器：创建websocket服务器的代码：

package nl.sajansen.screenchangenotifierserver

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.context.annotation.Configuration
import org.springframework.messaging.handler.annotation.MessageMapping
import org.springframework.messaging.simp.SimpMessagingTemplate
import org.springframework.messaging.simp.config.MessageBrokerRegistry
import org.springframework.scheduling.annotation.Scheduled
import org.springframework.stereotype.Controller
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker
import org.springframework.web.socket.config.annotation.StompEndpointRegistry
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer
import java.time.Instant
import java.time.format.DateTimeFormatter


@Configuration
@EnableWebSocketMessageBroker
class WebSocketConfig : WebSocketMessageBrokerConfigurer {
    override fun registerStompEndpoints(registry: StompEndpointRegistry) {
        registry.addEndpoint("/ws").setAllowedOrigins("*")
    }

    override fun configureMessageBroker(config: MessageBrokerRegistry) {
        config.enableSimpleBroker("/topic", "/queue")
        config.setApplicationDestinationPrefixes("/app")
    }
}

@Controller
class WebsocketController @Autowired constructor(val template: SimpMessagingTemplate) {
    @Scheduled(fixedDelayString = "1000")
    fun blastToClientsHostReport() {
        println("Sending something on the websocket")
        template.convertAndSend("/topic/greeting", "Hello World");
    }

    @MessageMapping("/greeting")
    fun handle(message: String): String {
        println("Received message: $message")
        template.convertAndSend("/topic/greeting", message)
        return "[" + getTimestamp() + ": " + message
    }
}

fun getTimestamp(): String = DateTimeFormatter.ISO_INSTANT.format(Instant.now())

Gradle依赖等：

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
    id("org.springframework.boot") version "2.1.9.RELEASE"
    id("io.spring.dependency-management") version "1.0.8.RELEASE"
    kotlin("jvm") version "1.2.71"
    kotlin("plugin.spring") version "1.2.71"
    kotlin("plugin.jpa") version "1.2.71"
    kotlin("plugin.allopen") version "1.2.71"       // For JPA lazy fetching
}

allOpen {
    annotation("javax.persistence.Entity")
    annotation("javax.persistence.Embeddable")
    annotation("javax.persistence.MappedSuperclass")
}

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-data-jpa")
    runtimeOnly("com.h2database:h2:1.4.197") // Fixed version as a workaround for https://github.com/h2database/h2database/issues/1841
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    testImplementation("org.springframework.boot:spring-boot-starter-test") {
        exclude(module = "junit")
        exclude(module = "mockito-core")
    }
    testImplementation("org.junit.jupiter:junit-jupiter-api")
    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine")
    testImplementation("com.ninja-squad:springmockk:1.1.2")
    compile("org.springframework.boot:spring-boot-starter-websocket")
}

tasks.withType<KotlinCompile> {
    kotlinOptions {
        freeCompilerArgs = listOf("-Xjsr305=strict")
        jvmTarget = "1.8"
    }
}

tasks.withType<Test> {
    useJUnitPlatform()
}

Python客户：

import random

import stomper as stomper
import websocket


def main():
  websocket.enableTrace(True)

  # Connecting to websocket
  ws = websocket.create_connection("ws://localhost:8080/ws")

  # Subscribing to topic
  client_id = str(random.randint(0, 1000))
  sub = stomper.subscribe("/topic/greeting", client_id, ack='auto')
  ws.send(sub)

  # Sending some message
  ws.send(stomper.send("/app/greeting", "Hello there"))

  while True:
    print("Receiving data: ")
    d = ws.recv()
    print(d)


if __name__ == '__main__':
  main()

Pip依赖项：

opencv-python==4.1.1.26
websocket-client==0.56.0
stomper==0.4.3

现在，服务器的控制台输出是这样的。可以看到，当客户端未连接时，没有订阅者发送预定消息。比客户端连接成功，预定消息被广播给1个订阅者。

Sending something on the websocket
2019-10-17 12:45:09.425 DEBUG 32285 --- [MessageBroker-3] org.springframework.web.SimpLogging      : Processing MESSAGE destination=/topic/greeting session=null payload=Hello World
Sending something on the websocket
2019-10-17 12:45:10.426 DEBUG 32285 --- [MessageBroker-3] org.springframework.web.SimpLogging      : Processing MESSAGE destination=/topic/greeting session=null payload=Hello World
2019-10-17 12:45:10.849  INFO 32285 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-10-17 12:45:10.850  INFO 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2019-10-17 12:45:10.850 DEBUG 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Detected StandardServletMultipartResolver
2019-10-17 12:45:10.855 DEBUG 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : enableLoggingRequestDetails='true': request parameters and headers will be shown which may lead to unsafe logging of potentially sensitive data
2019-10-17 12:45:10.855  INFO 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 5 ms
2019-10-17 12:45:10.861 DEBUG 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : GET "/ws", parameters={}
2019-10-17 12:45:10.865 DEBUG 32285 --- [nio-8080-exec-1] o.s.w.s.s.s.WebSocketHandlerMapping      : Mapped to org.springframework.web.socket.server.support.WebSocketHttpRequestHandler@27a9f025
2019-10-17 12:45:10.872 DEBUG 32285 --- [nio-8080-exec-1] o.s.w.s.s.s.WebSocketHttpRequestHandler  : GET /ws
2019-10-17 12:45:10.885 DEBUG 32285 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed 101 SWITCHING_PROTOCOLS
2019-10-17 12:45:10.901 DEBUG 32285 --- [nio-8080-exec-1] s.w.s.h.LoggingWebSocketHandlerDecorator : New StandardWebSocketSession[id=393fc3cd-9ca3-1749-1ea8-541def6592e0, uri=ws://localhost:8080/ws]
2019-10-17 12:45:10.912 DEBUG 32285 --- [nboundChannel-2] org.springframework.web.SimpLogging      : Processing SUBSCRIBE /topic/greeting id=216 session=393fc3cd-9ca3-1749-1ea8-541def6592e0
2019-10-17 12:45:10.914 DEBUG 32285 --- [nboundChannel-7] .WebSocketAnnotationMethodMessageHandler : Searching methods to handle SEND /app/greeting session=393fc3cd-9ca3-1749-1ea8-541def6592e0 text/plain payload=Hello there, lookupDestination='/greeting'
2019-10-17 12:45:10.915 DEBUG 32285 --- [nboundChannel-7] .WebSocketAnnotationMethodMessageHandler : Invoking nl.sajansen.screenchangenotifierserver.WebsocketController#handle[1 args]
Received message: Hello there
2019-10-17 12:45:10.916 DEBUG 32285 --- [nboundChannel-7] org.springframework.web.SimpLogging      : Processing MESSAGE destination=/topic/greeting session=null payload=Hello there
2019-10-17 12:45:10.916 DEBUG 32285 --- [nboundChannel-7] org.springframework.web.SimpLogging      : Broadcasting to 1 sessions.
2019-10-17 12:45:10.919 DEBUG 32285 --- [nboundChannel-7] org.springframework.web.SimpLogging      : Processing MESSAGE destination=/topic/greeting session=393fc3cd-9ca3-1749-1ea8-541def6592e0 payload=[2019-10-17T10:45:10.917Z: Hello there
2019-10-17 12:45:10.919 DEBUG 32285 --- [nboundChannel-7] org.springframework.web.SimpLogging      : Broadcasting to 1 sessions.
Sending something on the websocket
2019-10-17 12:45:11.427 DEBUG 32285 --- [MessageBroker-3] org.springframework.web.SimpLogging      : Processing MESSAGE destination=/topic/greeting session=null payload=Hello World

客户端的输出是这个，但只是等到世界末日才接收到消息：

--- request header ---
GET /ws HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Host: localhost:8080
Origin: http://localhost:8080
Sec-WebSocket-Key: 8ihHk0C5C0nji4s7u4atZQ==
Sec-WebSocket-Version: 13


-----------------------
--- response header ---
HTTP/1.1 101
Upgrade: websocket
Connection: upgrade
Sec-WebSocket-Accept: Drq8+/vJkXkvToB3/AuCGMdYwuo=
Date: Thu, 17 Oct 2019 10:45:10 GMT
-----------------------
send: b'\x81\xb9\x88k\xa6j\xdb>\xe49\xcb9\xef(\xcda\xcf\x0e\xb2Y\x97\\\x82\x0f\xc3\x19\xfc\x02\xc8\x0b\xfc\x02\xc9\x04\xb2D\xd2\x05\xf8\x02\xc5E\xef\x19\xc3\x0f\xfc\x02\xc8\r\x82\n\xc5\x01\xb2\n\xd3\x1e\xe7a\xacj\x82'
send: b'\x81\xc5\xd0\x8dE6\x83\xc8\x0br\xda\xe9 E\xa4\xe4+W\xa4\xe4*X\xea\xa2$F\xa0\xa2"D\xb5\xe81_\xbe\xeaOU\xbf\xe31S\xbe\xf9hB\xa9\xfd \x0c\xa4\xe8=B\xff\xfd)W\xb9\xe3O<\x98\xe8)Z\xbf\xad1^\xb5\xff 6\xda'
Receiving data:

如果您有更好的想法，请提供更多背景信息：更新将包含一个图像文件（可能编码为base64）。更新必须接近实时发送（允许延迟不超过1秒）。这些更新的间隔可以从几分钟到半秒不等。客户端和服务器是同一网络中的两台不同的机器，但该网络的吞吐量有限。

那么，谁能发现哪里出了问题？

我已经阅读了这个文档中关于websocket的大部分内容，但是我看不出哪里出了问题：https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html#websocket

这个答案也让我走得更远，但示例本身一开始就不起作用（在将而不是True更正为而True之后）。

2019年10月18日更新：我找了一个Python的SocketJS客户端，因为我得到了与SocketJS和JavaScript客户端一起工作的静态编程语言服务器部分。但是我找不到任何Python的SocketJS客户端实现…我想知道是否剩下的唯一解决方案是在Python应用程序（客户端）中启动websocket服务器，让客户端将其websocket服务器详细信息发送到静态编程语言服务器，然后该服务器将连接到客户端的websocket服务器。这不是一个漂亮的解决方案，但我想知道它是否有效。我会随时向您更新。

2021年2月1日更新：我没有花更多的时间来解决这个问题。但是我会让这篇文章成为万一有人解决了这个问题，并且可以帮助其他人解决这个问题。