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Add Server Streamable Http Transport #235

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2 changes: 1 addition & 1 deletion kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/Protocol.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -256,7 +256,7 @@ public abstract class Protocol(@PublishedApi internal val options: ProtocolOptio
JSONRPCResponse(
id = request.id,
error = JSONRPCError(
ErrorCode.Defined.MethodNotFound,
code = ErrorCode.Defined.MethodNotFound,
message = "Server does not support ${request.method}",
),
),
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12 changes: 8 additions & 4 deletions kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.kt
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Expand Up @@ -249,14 +249,14 @@ public data class JSONRPCNotification(
*/
@Serializable
public class JSONRPCResponse(
public val id: RequestId,
public val id: RequestId?,
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Suggested change
public val id: RequestId?,
public val id: RequestId? = null,

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According to the spec, the id is required field

public val jsonrpc: String = JSONRPC_VERSION,
public val result: RequestResult? = null,
public val error: JSONRPCError? = null,
) : JSONRPCMessage {

public fun copy(
id: RequestId = this.id,
id: RequestId? = this.id,
jsonrpc: String = this.jsonrpc,
result: RequestResult? = this.result,
error: JSONRPCError? = this.error,
Expand Down Expand Up @@ -292,8 +292,12 @@ public sealed interface ErrorCode {
* A response to a request that indicates an error occurred.
*/
@Serializable
public data class JSONRPCError(val code: ErrorCode, val message: String, val data: JsonObject = EmptyJsonObject) :
JSONRPCMessage
public data class JSONRPCError(
val id: RequestId? = null,
val code: ErrorCode,
val message: String,
val data: JsonObject = EmptyJsonObject,
) : JSONRPCMessage

/**
* Base interface for notification parameters with optional metadata.
Expand Down
27 changes: 27 additions & 0 deletions kotlin-sdk-server/api/kotlin-sdk-server.api
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Expand Up @@ -2,11 +2,20 @@ public final class io/modelcontextprotocol/kotlin/sdk/LibVersionKt {
public static final field LIB_VERSION Ljava/lang/String;
}

public abstract interface class io/modelcontextprotocol/kotlin/sdk/server/EventStore {
public abstract fun replayEventsAfter (Ljava/lang/String;Lkotlin/jvm/functions/Function3;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public abstract fun storeEvent (Ljava/lang/String;Lio/modelcontextprotocol/kotlin/sdk/JSONRPCMessage;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
}

public final class io/modelcontextprotocol/kotlin/sdk/server/KtorServerKt {
public static final fun MCP (Lio/ktor/server/application/Application;Lkotlin/jvm/functions/Function1;)V
public static final fun mcp (Lio/ktor/server/application/Application;Lkotlin/jvm/functions/Function1;)V
public static final fun mcp (Lio/ktor/server/routing/Routing;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)V
public static final fun mcp (Lio/ktor/server/routing/Routing;Lkotlin/jvm/functions/Function1;)V
public static final fun mcpStatelessStreamableHttp (Lio/ktor/server/application/Application;ZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;Lkotlin/jvm/functions/Function1;)V
public static synthetic fun mcpStatelessStreamableHttp$default (Lio/ktor/server/application/Application;ZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
public static final fun mcpStreamableHttp (Lio/ktor/server/application/Application;ZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;Lkotlin/jvm/functions/Function1;)V
public static synthetic fun mcpStreamableHttp$default (Lio/ktor/server/application/Application;ZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
}

public final class io/modelcontextprotocol/kotlin/sdk/server/RegisteredPrompt {
Expand Down Expand Up @@ -115,6 +124,24 @@ public final class io/modelcontextprotocol/kotlin/sdk/server/StdioServerTranspor
public fun start (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
}

public final class io/modelcontextprotocol/kotlin/sdk/server/StreamableHttpServerTransport : io/modelcontextprotocol/kotlin/sdk/shared/AbstractTransport {
public static final field STANDALONE_SSE_STREAM_ID Ljava/lang/String;
public fun <init> ()V
public fun <init> (ZZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;)V
public synthetic fun <init> (ZZLjava/util/List;Ljava/util/List;Lio/modelcontextprotocol/kotlin/sdk/server/EventStore;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
public fun close (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public final fun getSessionId ()Ljava/lang/String;
public final fun handleDeleteRequest (Lio/ktor/server/sse/ServerSSESession;Lio/ktor/server/application/ApplicationCall;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public final fun handleGetRequest (Lio/ktor/server/sse/ServerSSESession;Lio/ktor/server/application/ApplicationCall;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public final fun handlePostRequest (Lio/ktor/server/sse/ServerSSESession;Lio/ktor/server/application/ApplicationCall;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public final fun handleRequest (Lio/ktor/server/sse/ServerSSESession;Lio/ktor/server/application/ApplicationCall;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public fun send (Lio/modelcontextprotocol/kotlin/sdk/JSONRPCMessage;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public final fun setOnSessionClosed (Lkotlin/jvm/functions/Function1;)V
public final fun setOnSessionInitialized (Lkotlin/jvm/functions/Function1;)V
public final fun setSessionIdGenerator (Lkotlin/jvm/functions/Function0;)V
public fun start (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
}

public final class io/modelcontextprotocol/kotlin/sdk/server/WebSocketMcpKtorServerExtensionsKt {
public static final fun mcpWebSocket (Lio/ktor/server/routing/Route;Lio/modelcontextprotocol/kotlin/sdk/server/ServerOptions;Lkotlin/jvm/functions/Function2;)V
public static final fun mcpWebSocket (Lio/ktor/server/routing/Route;Ljava/lang/String;Lio/modelcontextprotocol/kotlin/sdk/server/ServerOptions;Lkotlin/jvm/functions/Function2;)V
Expand Down
129 changes: 129 additions & 0 deletions ...-sdk-server/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/KtorServer.kt
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Expand Up @@ -4,6 +4,7 @@ import io.github.oshai.kotlinlogging.KotlinLogging
import io.ktor.http.HttpStatusCode
import io.ktor.server.application.Application
import io.ktor.server.application.install
import io.ktor.server.request.header
import io.ktor.server.response.respond
import io.ktor.server.routing.Routing
import io.ktor.server.routing.RoutingContext
Expand All @@ -15,6 +16,7 @@ import io.ktor.server.sse.ServerSSESession
import io.ktor.server.sse.sse
import io.ktor.util.collections.ConcurrentMap
import io.ktor.utils.io.KtorDsl
import io.modelcontextprotocol.kotlin.sdk.ErrorCode

private val logger = KotlinLogging.logger {}

Expand Down Expand Up @@ -64,6 +66,51 @@ public fun Application.mcp(block: ServerSSESession.() -> Server) {
}
}

@KtorDsl
public fun Application.mcpStreamableHttp(
enableDnsRebindingProtection: Boolean = false,
allowedHosts: List<String>? = null,
allowedOrigins: List<String>? = null,
eventStore: EventStore? = null,
block: RoutingContext.() -> Server,
) {
val transports = ConcurrentMap<String, StreamableHttpServerTransport>()

routing {
post("/mcp") {
mcpStreamableHttpEndpoint(
transports,
enableDnsRebindingProtection,
allowedHosts,
allowedOrigins,
eventStore,
block,
)
}
}
}

@KtorDsl
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Missing KDoc

public fun Application.mcpStatelessStreamableHttp(
enableDnsRebindingProtection: Boolean = false,
allowedHosts: List<String>? = null,
allowedOrigins: List<String>? = null,
eventStore: EventStore? = null,
block: RoutingContext.() -> Server,
) {
routing {
post("/mcp") {
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get requests also need to be processed.

mcpStatelessStreamableHttpEndpoint(
enableDnsRebindingProtection,
allowedHosts,
allowedOrigins,
eventStore,
block,
)
}
}
}

private suspend fun ServerSSESession.mcpSseEndpoint(
postEndpoint: String,
transports: ConcurrentMap<String, SseServerTransport>,
Expand Down Expand Up @@ -94,6 +141,88 @@ internal fun ServerSSESession.mcpSseTransport(
return transport
}

private suspend fun RoutingContext.mcpStreamableHttpEndpoint(
transports: ConcurrentMap<String, StreamableHttpServerTransport>,
enableDnsRebindingProtection: Boolean = false,
allowedHosts: List<String>? = null,
allowedOrigins: List<String>? = null,
eventStore: EventStore? = null,
block: RoutingContext.() -> Server,
) {
val sessionId = this.call.request.header(MCP_SESSION_ID_HEADER)
val transport = if (sessionId != null && transports.containsKey(sessionId)) {
transports[sessionId]!!
} else if (sessionId == null) {
val transport = StreamableHttpServerTransport(
enableDnsRebindingProtection = enableDnsRebindingProtection,
allowedHosts = allowedHosts,
allowedOrigins = allowedOrigins,
eventStore = eventStore,
enableJsonResponse = true,
)

transport.setOnSessionInitialized { sessionId ->
transports[sessionId] = transport

logger.info { "New StreamableHttp connection established and stored with sessionId: $sessionId" }
}

val server = block()
server.onClose {
logger.info { "Server connection closed for sessionId: ${transport.sessionId}" }
}

server.connect(transport)

transport
} else {
null
}

if (transport == null) {
this.call.reject(
HttpStatusCode.BadRequest,
ErrorCode.Unknown(-32000),
"Bad Request: No valid session ID provided",
)
return
}

transport.handleRequest(null, this.call)
logger.debug { "Server connected to transport for sessionId: ${transport.sessionId}" }
}

private suspend fun RoutingContext.mcpStatelessStreamableHttpEndpoint(
enableDnsRebindingProtection: Boolean = false,
allowedHosts: List<String>? = null,
allowedOrigins: List<String>? = null,
eventStore: EventStore? = null,
block: RoutingContext.() -> Server,
) {
val transport = StreamableHttpServerTransport(
enableDnsRebindingProtection = enableDnsRebindingProtection,
allowedHosts = allowedHosts,
allowedOrigins = allowedOrigins,
eventStore = eventStore,
enableJsonResponse = true,
)
transport.setSessionIdGenerator(null)

logger.info { "New stateless StreamableHttp connection established without sessionId" }

val server = block()

server.onClose {
logger.info { "Server connection closed without sessionId" }
}

server.connect(transport)

transport.handleRequest(null, this.call)

logger.debug { "Server connected to transport without sessionId" }
}

internal suspend fun RoutingContext.mcpPostEndpoint(transports: ConcurrentMap<String, SseServerTransport>) {
val sessionId: String = call.request.queryParameters["sessionId"]
?: run {
Expand Down
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