diff --git a/Cargo.lock b/Cargo.lock
index 6acf5ec..25627c6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -506,6 +506,26 @@ version = "1.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
 
+[[package]]
+name = "pin-project"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fda4ed1c6c173e3fc7a83629421152e01d7b1f9b7f65fb301e490e8cfc656422"
+dependencies = [
+ "pin-project-internal",
+]
+
+[[package]]
+name = "pin-project-internal"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4359fd9c9171ec6e8c62926d6faaf553a8dc3f64e1507e76da7911b4f6a04405"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.13"
@@ -924,6 +944,7 @@ dependencies = [
  "futures",
  "hex",
  "log",
+ "pin-project",
  "serde",
  "serde_json",
  "tokio",
diff --git a/zvt/Cargo.toml b/zvt/Cargo.toml
index bfb70fe..e98a6ea 100644
--- a/zvt/Cargo.toml
+++ b/zvt/Cargo.toml
@@ -27,4 +27,5 @@ async-stream = "0.3.5"
 serde = { version = "1.0.185", features = ["derive"] }
 serde_json = "1.0.105"
 futures = "0.3.28"
+pin-project = "1.1.3"
 
diff --git a/zvt/src/feig/sequences.rs b/zvt/src/feig/sequences.rs
index 198ca69..35994b0 100644
--- a/zvt/src/feig/sequences.rs
+++ b/zvt/src/feig/sequences.rs
@@ -1,16 +1,15 @@
-use crate::sequences::{read_packet_async, write_packet_async, write_with_ack_async, Sequence};
-use crate::{packets, ZvtEnum, ZvtParser };
+use crate::sequences::DataSource;
+use crate::sequences::Sequence;
+use crate::{packets, ZvtEnum, ZvtParser};
 use anyhow::Result;
 use async_stream::try_stream;
 use std::boxed::Box;
 use std::collections::HashMap;
 use std::io::Seek;
 use std::io::{Error, ErrorKind};
-use std::marker::Unpin;
 use std::os::unix::fs::FileExt;
 use std::path::{Path, PathBuf};
 use std::pin::Pin;
-use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio_stream::Stream;
 use zvt_builder::ZVTError;
 
@@ -90,15 +89,12 @@ pub enum WriteFileResponse {
 }
 
 impl WriteFile {
-    pub fn into_stream<Source>(
+    pub fn into_stream(
         path: PathBuf,
         password: usize,
         adpu_size: u32,
-        src: &mut Source,
-    ) -> Pin<Box<impl Stream<Item = Result<WriteFileResponse>> + '_>>
-    where
-        Source: AsyncReadExt + AsyncWriteExt + Unpin,
-    {
+        src: &mut DataSource,
+    ) -> Pin<Box<impl Stream<Item = Result<WriteFileResponse>> + '_>> {
         // Protocol from the handbook (the numbering is not part of the handbook)
         // 1.1 ECR->PT: Send over the list of all files with their sizes.
         // 1.2 PT->ECR: Ack
@@ -133,25 +129,25 @@ impl WriteFile {
             };
 
             // 1.1. and 1.2
-            write_with_ack_async(&packet, &mut src).await?;
+            src.write_with_ack_async(&packet).await?;
             let mut buf = vec![0; adpu_size as usize];
             println!("the length is {}", buf.len());
 
             loop {
                 // Get the data.
-                let bytes = read_packet_async(&mut src).await?;
+                let bytes = src.read_packet_async().await?;
                 println!("The packet is {:?}", bytes);
 
                 let response = WriteFileResponse::zvt_parse(&bytes)?;
 
                 match response {
                     WriteFileResponse::CompletionData(_) => {
-                        write_packet_async(&mut src, &packets::Ack {}).await?;
+                        src.write_packet_async(&packets::Ack {}).await?;
                         yield response;
                         break;
                     }
                     WriteFileResponse::Abort(_) => {
-                        write_packet_async(&mut src, &packets::Ack {}).await?;
+                        src.write_packet_async(&packets::Ack {}).await?;
                         yield response;
                         break;
                     }
@@ -193,7 +189,7 @@ impl WriteFile {
                                 }),
                             }),
                         };
-                        write_packet_async(&mut src, &packet).await?;
+                        src.write_packet_async(&packet).await?;
 
                         yield response;
                     }
diff --git a/zvt/src/sequences.rs b/zvt/src/sequences.rs
index 8d24627..7aac968 100644
--- a/zvt/src/sequences.rs
+++ b/zvt/src/sequences.rs
@@ -7,7 +7,7 @@ use log::debug;
 use std::boxed::Box;
 use std::marker::Unpin;
 use std::pin::Pin;
-use tokio::io::{self, AsyncReadExt, AsyncWriteExt};
+use tokio::io::{self, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 
 pub async fn read_packet_async(src: &mut Pin<&mut impl AsyncReadExt>) -> Result<Vec<u8>> {
     let mut buf = vec![0; 3];
@@ -65,21 +65,41 @@ where
     Ok(())
 }
 
-struct DataSource<T>  
-    where T:  AsyncReadExt + AsyncWriteExt + Unpin {
-        s: T,
+trait AsyncReadWrite: AsyncRead + AsyncWrite + Unpin + Sync + Send {}
+
+#[pin_project::pin_project]
+pub struct DataSource {
+    #[pin]
+    s: Box<dyn AsyncReadWrite>,
+}
+
+impl DataSource {
+    pub async fn read_packet_async(self: Pin<&mut Self>) -> Result<Vec<u8>> {
+        let this = self.project();
+        let mut pinned_inner = this.s;
+        Ok(read_packet_async(&mut pinned_inner).await?)
     }
 
-// TODO(hrapp): I wanted to wrap the functions "write_packet_async" and "read_packet_async" into 
-// a struct that can take any `T` and has the more type "read_packet" and "write_packet". However I
-// completely failed to do so because of pin!(). How do I do that?!?
-impl<T> DataSource<T> 
-    where T:  AsyncReadExt + AsyncWriteExt + Unpin {
-        pub async fn read_packet_async(self: Pin<&mut Self>) -> Result<Vec<u8>> {
-            read_packet_async(self.s).await?
-        }
+    pub async fn write_packet_async<P>(self: Pin<&mut Self>, p: &P) -> Result<()>
+    where
+        P: ZvtSerializer + Sync + Send,
+        encoding::Default: encoding::Encoding<P>,
+    {
+        let this = self.project();
+        let mut pinned_inner = this.s;
+        Ok(write_packet_async(&mut pinned_inner, p).await?)
     }
 
+    pub async fn write_with_ack_async<P>(self: Pin<&mut Self>, p: &P) -> Result<()>
+    where
+        P: ZvtSerializer + Sync + Send,
+        encoding::Default: encoding::Encoding<P>,
+    {
+        let this = self.project();
+        let mut pinned_inner = this.s;
+        Ok(write_with_ack_async(&mut pinned_inner, p).await?)
+    }
+}
 
 /// The trait for converting a sequence into a stream.
 ///