diff --git a/src/bencode.rs b/src/bencode.rs
index 1673fce..42e8c14 100644
--- a/src/bencode.rs
+++ b/src/bencode.rs
@@ -1,2 +1,4 @@
 pub mod custom;
 pub mod de;
+pub mod ser;
+pub mod error;
diff --git a/src/bencode/de.rs b/src/bencode/de.rs
index 21cf60e..ad2f1fe 100644
--- a/src/bencode/de.rs
+++ b/src/bencode/de.rs
@@ -1,73 +1,6 @@
-use std::fmt;
-use std::fmt::Display;
-use std::str::Utf8Error;
-
-use serde::{de, Deserialize, ser};
+use serde::{de, Deserialize};
 use serde::de::{DeserializeSeed, MapAccess, SeqAccess, Visitor};
-
-pub type Result<T> = std::result::Result<T, Error>;
-
-#[derive(Debug, PartialEq)]
-pub enum Error {
-    Message(String),
-
-    WontImplement,
-    Eof,
-    Syntax,
-    InvalidUtf8,
-    ExpectedBytes,
-    ExpectedBytesSep,
-    ExpectedNumbers,
-    ExpectedInteger,
-    ExpectedIntegerEnd,
-    ExpectedList,
-    ExpectedListEnd,
-    ExpectedDict,
-    ExpectedDictEnd,
-    TrailingCharacters,
-}
-
-impl ser::Error for Error {
-    fn custom<T: Display>(msg: T) -> Self {
-        Error::Message(msg.to_string())
-    }
-}
-
-impl de::Error for Error {
-    fn custom<T: Display>(msg: T) -> Self {
-        Error::Message(msg.to_string())
-    }
-}
-
-impl From<Utf8Error> for Error {
-    fn from(_: Utf8Error) -> Self {
-        Error::InvalidUtf8
-    }
-}
-
-impl Display for Error {
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            Error::Message(msg) => formatter.write_str(msg),
-            Error::WontImplement => formatter.write_str("there is no reasonable way to deserialize to this type"),
-            Error::Eof => formatter.write_str("unexpected end of input"),
-            Error::Syntax => formatter.write_str("syntax error"),
-            Error::InvalidUtf8 => formatter.write_str("could not decoded as UTF-8"),
-            Error::ExpectedBytes => formatter.write_str("expected byte string start char: any number"),
-            Error::ExpectedBytesSep => formatter.write_str("expected byte separator char: ':'"),
-            Error::ExpectedInteger => formatter.write_str("expected integer start char 'i'"),
-            Error::ExpectedNumbers => formatter.write_str("expected numbers"),
-            Error::ExpectedIntegerEnd => formatter.write_str("expected integer end char 'e'"),
-            Error::ExpectedList => formatter.write_str("expected list start char 'l'"),
-            Error::ExpectedListEnd => formatter.write_str("expected list end char 'e'"),
-            Error::ExpectedDict => formatter.write_str("expected dict start char 'd'"),
-            Error::ExpectedDictEnd => formatter.write_str("expected dict end char 'e'"),
-            Error::TrailingCharacters => formatter.write_str("trailing characters")
-        }
-    }
-}
-
-impl std::error::Error for Error {}
+use crate::bencode::error::{Error, Result};
 
 pub struct Deserializer<'de> {
     input: &'de [u8],
@@ -505,8 +438,8 @@ mod test {
     use std::collections::HashMap;
 
     use serde::Deserialize;
-
-    use crate::de::{Error, from_bytes, from_str};
+    use crate::bencode::de::{from_bytes, from_str};
+    use crate::bencode::error::Error;
 
     #[test]
     fn test_int() {
diff --git a/src/bencode/error.rs b/src/bencode/error.rs
new file mode 100644
index 0000000..3d1ceb6
--- /dev/null
+++ b/src/bencode/error.rs
@@ -0,0 +1,68 @@
+use std::fmt::Display;
+use std::fmt;
+use std::str::Utf8Error;
+use serde::{de, ser};
+
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    Message(String),
+
+    WontImplement,
+    Eof,
+    Syntax,
+    InvalidUtf8,
+    ExpectedBytes,
+    ExpectedBytesSep,
+    ExpectedNumbers,
+    ExpectedInteger,
+    ExpectedIntegerEnd,
+    ExpectedList,
+    ExpectedListEnd,
+    ExpectedDict,
+    ExpectedDictEnd,
+    TrailingCharacters,
+}
+
+impl ser::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl de::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl From<Utf8Error> for Error {
+    fn from(_: Utf8Error) -> Self {
+        Error::InvalidUtf8
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Message(msg) => formatter.write_str(msg),
+            Error::WontImplement => formatter.write_str("there is no reasonable way to (de)serialize this type"),
+            Error::Eof => formatter.write_str("unexpected end of input"),
+            Error::Syntax => formatter.write_str("syntax error"),
+            Error::InvalidUtf8 => formatter.write_str("could not decoded as UTF-8"),
+            Error::ExpectedBytes => formatter.write_str("expected byte string start char: any number"),
+            Error::ExpectedBytesSep => formatter.write_str("expected byte separator char: ':'"),
+            Error::ExpectedInteger => formatter.write_str("expected integer start char 'i'"),
+            Error::ExpectedNumbers => formatter.write_str("expected numbers"),
+            Error::ExpectedIntegerEnd => formatter.write_str("expected integer end char 'e'"),
+            Error::ExpectedList => formatter.write_str("expected list start char 'l'"),
+            Error::ExpectedListEnd => formatter.write_str("expected list end char 'e'"),
+            Error::ExpectedDict => formatter.write_str("expected dict start char 'd'"),
+            Error::ExpectedDictEnd => formatter.write_str("expected dict end char 'e'"),
+            Error::TrailingCharacters => formatter.write_str("trailing characters")
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+pub type Result<T> = std::result::Result<T, Error>;
diff --git a/src/bencode/ser.rs b/src/bencode/ser.rs
new file mode 100644
index 0000000..fc4a8cc
--- /dev/null
+++ b/src/bencode/ser.rs
@@ -0,0 +1,361 @@
+use std::collections::BTreeMap;
+
+use serde::{ser, Serialize};
+
+use crate::bencode::error::{Error, Result};
+
+pub struct Serializer {
+    output: Vec<u8>,
+}
+
+pub fn to_bytes<T>(value: &T) -> Result<Vec<u8>>
+where
+    T: Serialize + ?Sized
+{
+    let mut serializer = Serializer{
+        output: Vec::new(),
+    };
+    value.serialize(&mut serializer)?;
+    Ok(serializer.output)
+}
+
+pub fn to_string<T>(value: &T) -> Result<String>
+where
+    T: Serialize
+{
+    let bytes = to_bytes(value)?;
+    Ok(std::str::from_utf8(&bytes[..])?.to_string())
+}
+
+
+
+impl<'a> ser::Serializer for &'a mut Serializer
+{
+    type Ok = ();
+
+    type Error = Error;
+
+    type SerializeSeq = Self;
+    type SerializeTuple = Self;
+    type SerializeTupleStruct = Self;
+    type SerializeTupleVariant = Self;
+    type SerializeMap = Self;
+    type SerializeStruct = Self;
+    type SerializeStructVariant = Self;
+
+    fn serialize_bool(self, v: bool) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_i8(self, v: i8) -> Result<()> {
+        self.output.extend(format!("i{v}e").into_bytes());
+        Ok(())
+    }
+
+    fn serialize_i16(self, v: i16) -> Result<()> {
+        self.output.extend(format!("i{v}e").into_bytes());
+        Ok(())
+    }
+
+    fn serialize_i32(self, v: i32) -> Result<()> {
+        self.output.extend(format!("i{v}e").into_bytes());
+        Ok(())
+    }
+
+    fn serialize_i64(self, v: i64) -> Result<()> {
+        self.output.extend(format!("i{v}e").into_bytes());
+        Ok(())
+    }
+
+    fn serialize_i128(self, v: i128) -> Result<()> {
+        self.output.extend(format!("i{v}e").into_bytes());
+        Ok(())
+    }
+
+    fn serialize_u8(self, v: u8) -> Result<()> {
+        todo!()
+    }
+
+    fn serialize_u16(self, _v: u16) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_u32(self, _v: u32) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_u64(self, _v: u64) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_u128(self, _v: u128) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_f32(self, _v: f32) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_f64(self, _v: f64) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_char(self, v: char) -> Result<()> {
+        self.output.extend(format!("{}:", v.len_utf8()).into_bytes());
+        let mut b = [0; 4];
+        v.encode_utf8(&mut b);
+        self.output.extend(&b[..v.len_utf8()]);
+        Ok(())
+    }
+
+    fn serialize_str(self, v: &str) -> Result<()> {
+        self.output.extend(format!("{}:", v.len()).into_bytes());
+        self.output.extend(v.as_bytes());
+        Ok(())
+    }
+
+    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
+        self.output.extend(format!("{}:", v.len()).into_bytes());
+        self.output.extend(v);
+        Ok(())
+    }
+
+    fn serialize_none(self) -> Result<()> {
+        todo!()
+    }
+
+    fn serialize_some<T>(self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        todo!()
+    }
+
+    fn serialize_unit(self) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_unit_variant(self, _name: &'static str, _variant_index: u32, _variant: &'static str) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_newtype_variant<T>(self, name: &'static str, variant_index: u32, variant: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
+        self.output.push('l' as u8);
+        Ok(self)
+    }
+
+    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
+        println!("tuple");
+        todo!()
+    }
+
+    fn serialize_tuple_struct(self, _name: &'static str, _len: usize) -> Result<Self::SerializeTupleStruct> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_tuple_variant(self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize) -> Result<Self::SerializeTupleVariant> {
+        Err(Error::WontImplement)
+    }
+
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
+        self.output.push('d' as u8);
+        Ok(self)
+    }
+
+    fn serialize_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
+        todo!()
+    }
+
+    fn serialize_struct_variant(self, _name: &'static str, _variant_index: u32, _variant: &'static str, _len: usize) -> Result<Self::SerializeStructVariant> {
+        Err(Error::WontImplement)
+    }
+}
+
+impl <'a> ser::SerializeSeq for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<()> {
+        self.output.push('e' as u8);
+        Ok(())
+    }
+}
+
+impl <'a> ser::SerializeTuple for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        todo!()
+    }
+
+    fn end(self) -> Result<()> {
+        todo!()
+    }
+}
+
+impl <'a> ser::SerializeTupleStruct for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        Err(Error::WontImplement)
+    }
+
+    fn end(self) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+}
+
+impl <'a> ser::SerializeTupleVariant for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        Err(Error::WontImplement)
+    }
+
+    fn end(self) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+}
+
+impl <'a> ser::SerializeMap for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        key.serialize(&mut **self)
+    }
+
+    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<()> {
+        // TODO serialize only here and sort first
+        self.output.push('e' as u8);
+        Ok(())
+    }
+}
+
+impl <'a> ser::SerializeStruct for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        todo!()
+    }
+
+    fn end(self) -> Result<()> {
+        self.output.push('e' as u8);
+        Ok(())
+    }
+}
+
+impl <'a> ser::SerializeStructVariant for &'a mut Serializer {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize
+    {
+        Err(Error::WontImplement)
+    }
+
+    fn end(self) -> Result<()> {
+        Err(Error::WontImplement)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::collections::HashMap;
+
+    use crate::bencode::ser::to_string;
+
+    #[test]
+    fn test_int() {
+        assert_eq!(to_string(&42).unwrap(), "i42e");
+        assert_eq!(to_string(&13).unwrap(), "i13e");
+    }
+
+    #[test]
+    fn test_char() {
+        assert_eq!(to_string(&'b').unwrap(), "1:b");
+        assert_eq!(to_string(&'💩').unwrap(), "4:💩");
+    }
+
+    #[test]
+    fn test_str() {
+        assert_eq!(to_string(&"foo").unwrap(), "3:foo");
+        assert_eq!(to_string(&"bar").unwrap(), "3:bar");
+        assert_eq!(to_string(&"foo💩").unwrap(), "7:foo💩");
+    }
+
+    #[test]
+    fn test_seq() {
+        assert_eq!(to_string(&vec![42, 13, 7]).unwrap(), "li42ei13ei7ee");
+        assert_eq!(to_string(&vec!["foo", "bar", "💩"]).unwrap(), "l3:foo3:bar4:💩e");
+    }
+
+    #[test]
+    fn test_map() {
+        assert_eq!(to_string(&HashMap::from([
+            ("foo", 42),
+            ("bar", 13),
+        ])).unwrap(),
+            "d3:bari13e3:fooi42ee"
+        );
+        assert_eq!(to_string(&HashMap::from([
+            ("foo", "💩"),
+            ("bar", "🙈"),
+        ])).unwrap(),
+            "d3:bar4:🙈3:foo4:💩e"
+        );
+    }
+}