diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..ed1faa2
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,34 @@
+
+pub enum ErrorKind {
+    InvalidEndpoint,
+    JsonParseError,
+}
+
+pub struct Error {
+    kind: ErrorKind,
+}
+
+impl Error {
+    pub fn new(kind: ErrorKind) -> Error {
+        Error {
+            kind,
+        }
+    }
+}
+
+impl From<serde_json::Error> for Error {
+    fn from(_: serde_json::Error) -> Self {
+        Error {
+            kind: ErrorKind::JsonParseError,
+        }
+    }
+}
+
+impl ToString for Error {
+    fn to_string(&self) -> String {
+        match self.kind {
+            ErrorKind::InvalidEndpoint => "invalid endpoint",
+            ErrorKind::JsonParseError => "JSON parse error",
+        }.to_string()
+    }
+}
diff --git a/src/http/handler.rs b/src/http/handler.rs
index 1deb136..8515d8a 100644
--- a/src/http/handler.rs
+++ b/src/http/handler.rs
@@ -88,8 +88,6 @@ fn endpoint_handler(
     res: &mut super::Response,
     endpoint: &str,
 ) {
-    let mut buf = [0; 8192];
-
     res.add_header("Cache-Control", "no-store");
 
     let mut error = |code: u16, err_str: &str, client: &mut super::HttpStream| {
@@ -97,10 +95,21 @@ fn endpoint_handler(
         res.status(code);
         res.error_info(err_str.to_string());
 
+        let mut obj = serde_json::Value::Object(serde_json::Map::new());
+        obj["status"] = serde_json::Value::String("error".to_string());
+        obj["message"] = serde_json::Value::String(err_str.to_string());
+        let buf = obj.to_string() + "\r\n";
+
+        let length = buf.as_bytes().len();
+        res.add_header("Content-Length", length.to_string().as_str());
+        res.add_header("Content-Type", "application/json; charset=utf-8");
+
         if let Err(e) = res.send(&mut client.stream) {
             println!("Unable to send: {}", e);
             client.server_keep_alive = false;
         }
+
+        client.stream.write_all(buf.as_bytes());
     };
 
     let length = req.find_header("Content-Length");
@@ -126,6 +135,7 @@ fn endpoint_handler(
         }
     };
 
+    let mut buf = [0; 8192];
     client.stream.read_exact(&mut buf[..length]);
 
     // TODO decompress
@@ -142,7 +152,7 @@ fn endpoint_handler(
 
     let buf = match usimp::endpoint(endpoint, input) {
         Ok(output) => output.to_string() + "\r\n",
-        Err(e) => format!("{{\"status\":\"error\",\"message\":\"{}\"}}\r\n", e),
+        Err(e) => return error(500, e.to_string().as_str(), client),
     };
 
     // TODO compress
diff --git a/src/main.rs b/src/main.rs
index 1bd8744..9feac3e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,15 +1,17 @@
+use std::net::{SocketAddr, TcpListener, UdpSocket};
+use std::sync::Arc;
+use std::sync::Mutex;
+use std::thread;
+
+use openssl::ssl::{SslAcceptor, SslFiletype, SslMethod};
+use threadpool::ThreadPool;
+
 mod database;
 mod http;
 mod udp;
 mod usimp;
 mod websocket;
-
-use openssl::ssl::{SslAcceptor, SslFiletype, SslMethod};
-use std::net::{SocketAddr, TcpListener, UdpSocket};
-use std::sync::Arc;
-use std::sync::Mutex;
-use std::thread;
-use threadpool::ThreadPool;
+mod error;
 
 enum SocketType {
     Http,
diff --git a/src/usimp/mod.rs b/src/usimp/mod.rs
index 3561b81..867939c 100644
--- a/src/usimp/mod.rs
+++ b/src/usimp/mod.rs
@@ -1,11 +1,13 @@
-use crate::database;
 use serde::{Deserialize, Serialize};
 use serde_json;
 
-pub fn endpoint(endpoint: &str, input: serde_json::Value) -> serde_json::Result<serde_json::Value> {
+use crate::database;
+use crate::error::*;
+
+pub fn endpoint(endpoint: &str, input: serde_json::Value) -> Result<serde_json::Value, Error> {
     match endpoint {
         "echo" => Ok(serde_json::to_value(echo(serde_json::from_value(input)?))?),
-        _ => Ok("{}".into()),
+        _ => Err(Error::new(ErrorKind::InvalidEndpoint)),
     }
 }