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Fix: Handle SSE ping messages in WebFluxSseClientTransport #272

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Fix: Handle SSE ping messages in WebFluxSseClientTransport #272

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3b30f50
Fix: Handle SSE ping messages in WebFluxSseClientTransport
goecho May 28, 2025
c768c74
Refactor: Improve SSE ping comment handling and generalize to isComme…
goecho Jul 25, 2025
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32 changes: 24 additions & 8 deletions ...lux/src/main/java/io/modelcontextprotocol/client/transport/WebFluxSseClientTransport.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,19 +3,20 @@
*/
package io.modelcontextprotocol.client.transport;

import java.io.IOException;
import java.util.function.BiConsumer;
import java.util.function.Function;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import io.micrometer.common.util.StringUtils;
import io.modelcontextprotocol.spec.McpClientTransport;
import io.modelcontextprotocol.spec.McpError;
import io.modelcontextprotocol.spec.McpSchema;
import io.modelcontextprotocol.spec.McpSchema.JSONRPCMessage;
import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.MediaType;
import org.springframework.http.codec.ServerSentEvent;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.Disposable;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
Expand All @@ -25,10 +26,9 @@
import reactor.util.retry.Retry;
import reactor.util.retry.Retry.RetrySignal;

import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.MediaType;
import org.springframework.http.codec.ServerSentEvent;
import org.springframework.web.reactive.function.client.WebClient;
import java.io.IOException;
import java.util.function.BiConsumer;
import java.util.function.Function;

/**
* Server-Sent Events (SSE) implementation of the
Expand Down Expand Up @@ -166,6 +166,18 @@ public WebFluxSseClientTransport(WebClient.Builder webClientBuilder, ObjectMappe
this.sseEndpoint = sseEndpoint;
}

private boolean isCommentLine(ServerSentEvent<String> event) {
String id = event.id();
String type = event.event();
String data = event.data();
String comment = event.comment();

return StringUtils.isEmpty(id) &&
StringUtils.isEmpty(type) &&
StringUtils.isEmpty(data) &&
comment != null;
}

/**
* Establishes a connection to the MCP server using Server-Sent Events (SSE). This
* method initiates the SSE connection and sets up the message processing pipeline.
Expand Down Expand Up @@ -212,6 +224,10 @@ else if (MESSAGE_EVENT_TYPE.equals(event.event())) {
s.error(ioException);
}
}
else if (isCommentLine(event)) {
logger.debug("Received SSE comment: {}", event.comment());
s.complete();
}
else {
s.error(new McpError("Received unrecognized SSE event type: " + event.event()));
}
Expand Down