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Fix: Buffer stdout data to handle large/fragmented JSON responses #22

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Fix: Buffer stdout data to handle large/fragmented JSON responses #22

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43 changes: 27 additions & 16 deletions src/mcp-client.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ export class MCPClient {

async connect(): Promise<void> {
logger.debug("[MCP Client] Starting connection...");

try {
const spawnOptions: any = {
stdio: ['pipe', 'pipe', 'pipe']
Expand All @@ -38,7 +38,7 @@ export class MCPClient {
}

logger.debug(`[MCP Client] Spawning process: ${this.serverParams.command} ${this.serverParams.args?.join(' ')}`);

this.process = spawn(
this.serverParams.command,
this.serverParams.args || [],
Expand All @@ -62,10 +62,21 @@ export class MCPClient {
logger.info(`[MCP Client] Process exited with code ${code}`);
});


let stdoutBuffer = '';
if (this.stdout) {
this.stdout.on('data', (data: Buffer) => {
logger.debug(`[MCP Client] Received raw data: ${data.toString().trim()}`);
this.handleResponse(data);
const chunk = data.toString();
logger.debug(`[MCP Client] Received raw data: ${chunk.trim()}`);
stdoutBuffer += chunk;
let newlineIndex;
while ((newlineIndex = stdoutBuffer.indexOf('\n')) !== -1) {
const message = stdoutBuffer.slice(0, newlineIndex);
stdoutBuffer = stdoutBuffer.slice(newlineIndex + 1);
if (message.trim()) {
this.handleResponse(Buffer.from(message));
}
}
});
}

Expand Down Expand Up @@ -96,7 +107,7 @@ export class MCPClient {
name: "MCPLLMBridge",
version: "1.0.0"
};

const initMessage = {
jsonrpc: "2.0",
method: "initialize",
Expand All @@ -110,7 +121,7 @@ export class MCPClient {

try {
const response = await this.sendMessage(initMessage);

if (!response || typeof response.protocolVersion !== 'string') {
throw new Error('[MCP Client] Invalid initialization response from server');
}
Expand Down Expand Up @@ -145,12 +156,12 @@ export class MCPClient {

private handleResponse(data: Buffer) {
const messages = data.toString().split('\n').filter(line => line.trim());

for (const message of messages) {
try {
const response = JSON.parse(message);
logger.debug(`[MCP Client] Parsed message: ${JSON.stringify(response)}`);

const pendingMessage = this.messageQueue.find(m => m.message.id === response.id);
if (pendingMessage) {
if (response.error) {
Expand Down Expand Up @@ -179,17 +190,17 @@ export class MCPClient {
if (message.id !== undefined) {
this.messageQueue.push({ resolve, reject, message });
}

const messageStr = JSON.stringify(message) + '\n';
logger.debug(`[MCP Client] Sending message: ${messageStr.trim()}`);

this.stdin.write(messageStr, (error) => {
if (error) {
logger.error(`[MCP Client] Failed to send message: ${error.message}`);
reject(error);
return;
}

// If it's a notification (no id), resolve immediately
if (message.id === undefined) {
resolve(undefined);
Expand All @@ -204,7 +215,7 @@ export class MCPClient {
}

logger.debug("[MCP Client] Requesting available tools");

try {
const message = {
jsonrpc: "2.0",
Expand All @@ -228,7 +239,7 @@ export class MCPClient {
}

logger.debug(`[MCP Client] Calling tool '${toolName}' with args: ${JSON.stringify(toolArgs)}`);

// Check if the tool exists
if (!this.availableTools.has(toolName)) {
logger.error(`[MCP Client] Unknown tool '${toolName}'. Available tools: ${Array.from(this.availableTools).join(', ')}`);
Expand Down Expand Up @@ -257,17 +268,17 @@ export class MCPClient {

async close(): Promise<void> {
logger.debug("[MCP Client] Closing connection...");

if (this.process) {
this.process.kill();
this.process = null;
}

this.stdin = null;
this.stdout = null;
this.initialized = false;
this.availableTools.clear();

logger.debug("[MCP Client] Connection closed");
}
}