refactor(transport): make fields final and specify charset in stream readers

Make scheduler fields final in client and server transports for better immutability.
Explicitly specify UTF-8 charset when creating InputStreamReader instances to ensure consistent character encoding.

Author: codeboyzhou

mcp-core/src/main/java/io/modelcontextprotocol/client/transport/StdioClientTransport.java

@@ -48,16 +48,16 @@ public class StdioClientTransport implements McpClientTransport {
 	/** The server process being communicated with */
 	private Process process;
 
-	private McpJsonMapper jsonMapper;
+	private final McpJsonMapper jsonMapper;
 
 	/** Scheduler for handling inbound messages from the server process */
-	private Scheduler inboundScheduler;
+	private final Scheduler inboundScheduler;
 
 	/** Scheduler for handling outbound messages to the server process */
-	private Scheduler outboundScheduler;
+	private final Scheduler outboundScheduler;
 
 	/** Scheduler for handling error messages from the server process */
-	private Scheduler errorScheduler;
+	private final Scheduler errorScheduler;
 
 	/** Parameters for configuring and starting the server process */
 	private final ServerParameters params;
@@ -180,7 +180,7 @@ public void awaitForExit() {
 	private void startErrorProcessing() {
 		this.errorScheduler.schedule(() -> {
 			try (BufferedReader processErrorReader = new BufferedReader(
-					new InputStreamReader(process.getErrorStream()))) {
+					new InputStreamReader(process.getErrorStream(), StandardCharsets.UTF_8))) {
 				String line;
 				while (!isClosing && (line = processErrorReader.readLine()) != null) {
 					try {
@@ -246,7 +246,8 @@ public Mono<Void> sendMessage(JSONRPCMessage message) {
 	 */
 	private void startInboundProcessing() {
 		this.inboundScheduler.schedule(() -> {
-			try (BufferedReader processReader = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
+			try (BufferedReader processReader = new BufferedReader(
+					new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8))) {
 				String line;
 				while (!isClosing && (line = processReader.readLine()) != null) {
 					try {

mcp-core/src/main/java/io/modelcontextprotocol/server/transport/StdioServerTransportProvider.java

@@ -10,7 +10,6 @@
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.nio.charset.StandardCharsets;
-import java.util.List;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
@@ -22,7 +21,6 @@
 import io.modelcontextprotocol.spec.McpServerSession;
 import io.modelcontextprotocol.spec.McpServerTransport;
 import io.modelcontextprotocol.spec.McpServerTransportProvider;
-import io.modelcontextprotocol.spec.ProtocolVersions;
 import io.modelcontextprotocol.util.Assert;
 import io.modelcontextprotocol.json.McpJsonMapper;
 import org.slf4j.Logger;
@@ -82,11 +80,6 @@ public StdioServerTransportProvider(McpJsonMapper jsonMapper, InputStream inputS
 		this.outputStream = outputStream;
 	}
 
-	@Override
-	public List<String> protocolVersions() {
-		return List.of(ProtocolVersions.MCP_2024_11_05);
-	}
-
 	@Override
 	public void setSessionFactory(McpServerSession.Factory sessionFactory) {
 		// Create a single session for the stdio connection
@@ -124,10 +117,10 @@ private class StdioMcpSessionTransport implements McpServerTransport {
 		private final AtomicBoolean isStarted = new AtomicBoolean(false);
 
 		/** Scheduler for handling inbound messages */
-		private Scheduler inboundScheduler;
+		private final Scheduler inboundScheduler;
 
 		/** Scheduler for handling outbound messages */
-		private Scheduler outboundScheduler;
+		private final Scheduler outboundScheduler;
 
 		private final Sinks.One<Void> outboundReady = Sinks.one();
 
@@ -198,9 +191,9 @@ private void startInboundProcessing() {
 			if (isStarted.compareAndSet(false, true)) {
 				this.inboundScheduler.schedule(() -> {
 					inboundReady.tryEmitValue(null);
-					BufferedReader reader = null;
+					BufferedReader reader;
 					try {
-						reader = new BufferedReader(new InputStreamReader(inputStream));
+						reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
 						while (!isClosing.get()) {
 							try {
 								String line = reader.readLine();