diff --git a/src/flow/adjacencies.rs b/src/flow/adjacencies.rs
index 7736517..0f0979a 100644
--- a/src/flow/adjacencies.rs
+++ b/src/flow/adjacencies.rs
@@ -2,7 +2,6 @@ use crate::flow::Node;
 use crate::types::{Address, Edge, U256};
 use std::cmp::Reverse;
 use std::collections::HashMap;
-use std::collections::HashSet;
 
 pub struct Adjacencies<'a> {
     edges: &'a HashMap<Address, Vec<Edge>>,
diff --git a/src/flow/flow.rs b/src/flow/flow.rs
index d49e522..616d5df 100644
--- a/src/flow/flow.rs
+++ b/src/flow/flow.rs
@@ -5,7 +5,11 @@ use std::cmp::min;
 use std::collections::HashMap;
 use std::collections::VecDeque;
 
-pub fn compute_flow(source: &Address, sink: &Address, edges: &HashMap<Address, Vec<Edge>>) {
+pub fn compute_flow(
+    source: &Address,
+    sink: &Address,
+    edges: &HashMap<Address, Vec<Edge>>,
+) -> String {
     let mut adjacencies = Adjacencies::new(edges);
     let mut used_edges: HashMap<Node, HashMap<Node, U256>> = HashMap::new();
 
@@ -39,6 +43,7 @@ pub fn compute_flow(source: &Address, sink: &Address, edges: &HashMap<Address, V
         }
     }
     println!("Max flow: {flow}");
+    flow.to_string()
 }
 
 fn augmenting_path(
diff --git a/src/io.rs b/src/io.rs
index c6b7060..b7f860d 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -1,5 +1,4 @@
 use std::collections::HashMap;
-use std::collections::HashSet;
 use std::fs::File;
 use std::io;
 use std::io::Read;
diff --git a/src/main.rs b/src/main.rs
index 851d669..6e72f5a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,10 +5,15 @@ mod io;
 mod server;
 mod types;
 
-use types::Address;
+use server::Server;
 
 fn main() {
-    server::start(8080);
+    let port = if env::args().len() == 1 {
+        8080
+    } else {
+        env::args().nth(1).unwrap().as_str().parse::<u16>().unwrap()
+    };
+    Server::start(port);
 
     // let args: Vec<String> = env::args().collect();
     // if args.len() != 4 {
diff --git a/src/server.rs b/src/server.rs
index 4ccbe4b..86995e3 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -1,24 +1,20 @@
-use json;
+use crate::flow;
+use crate::io::read_edges_binary;
+use crate::types::{Address, Edge};
 use json::JsonValue;
+use std::collections::HashMap;
 use std::error::Error;
-use std::io::{BufRead, BufReader, ErrorKind};
+use std::io::{BufRead, BufReader, Write};
+use std::sync::Arc;
+use std::thread;
 use std::{
-    io::{Read, Write},
-    net::{SocketAddr, TcpListener, TcpStream},
+    io::Read,
+    net::{TcpListener, TcpStream},
 };
 
-pub fn start(port: u16) {
-    let listener =
-        TcpListener::bind(format!("127.0.0.1:{port}")).expect("Could not create server.");
-    loop {
-        match listener.accept() {
-            Ok((socket, address)) => match handle_connection(socket, address) {
-                Ok(_) => {}
-                Err(e) => println!("Error communicating with client: {e}"),
-            },
-            Err(e) => println!("Error accepting connection: {e}"),
-        }
-    }
+pub struct Server {
+    edges: Arc<HashMap<Address, Vec<Edge>>>,
+    //threads: Vec<thread::JoinHandle<()>>,
 }
 
 struct JsonRpcRequest {
@@ -27,19 +23,66 @@ struct JsonRpcRequest {
     params: JsonValue,
 }
 
-fn handle_connection(mut socket: TcpStream, address: SocketAddr) -> Result<(), Box<dyn Error>> {
-    let request = read_request(socket)?;
-    match request.method.as_str() {
-        "load_edges_binary" => {}
-        "compute_transfer" => {}
-        "cancel" => {}
-        "update_edges" => {}
-        _ => {}
+impl Server {
+    pub fn start(port: u16) {
+        let mut server = Server {
+            edges: Arc::new(HashMap::new()),
+            //threads: Vec::new(),
+        };
+
+        let listener =
+            TcpListener::bind(format!("127.0.0.1:{port}")).expect("Could not create server.");
+        loop {
+            match listener.accept() {
+                Ok((socket, _)) => match server.handle_connection(socket) {
+                    Ok(_) => {}
+                    Err(e) => println!("Error communicating with client: {e}"),
+                },
+                Err(e) => println!("Error accepting connection: {e}"),
+            }
+        }
+    }
+
+    fn handle_connection(&mut self, mut socket: TcpStream) -> Result<(), Box<dyn Error>> {
+        let request = read_request(&mut socket)?;
+        match request.method.as_str() {
+            "load_edges_binary" => {
+                // TODO do this in its own thread?
+                let edges = read_edges_binary(&request.params["file"].to_string())?;
+                self.edges = Arc::new(edges);
+                socket.write_all(jsonrpc_result(request.id, self.edges.len()).as_bytes())?;
+            }
+            "compute_transfer" => {
+                // TODO limit number of threads
+                let edges = self.edges.clone();
+                let _thread = thread::spawn(move || {
+                    println!("Computing flow");
+                    let flow = flow::compute_flow(
+                        &Address::from(request.params["from"].to_string().as_str()),
+                        &Address::from(request.params["to"].to_string().as_str()),
+                        //&U256::from(request.params["value"].to_string().as_str()),
+                        edges.as_ref(),
+                    );
+                    println!("Computed flow");
+                    // TODO error handling
+                    socket
+                        .write_all(
+                            jsonrpc_result(request.id, json::JsonValue::from(flow)).as_bytes(),
+                        )
+                        .unwrap();
+                });
+                //self.threads.push(thread);
+            }
+            "cancel" => {}
+            "update_edges" => {}
+            // TODO error handling
+            _ => {}
+        }
+        Ok(())
     }
-    Ok(())
 }
 
-fn read_request(mut socket: TcpStream) -> Result<JsonRpcRequest, Box<dyn Error>> {
+fn read_request(socket: &mut TcpStream) -> Result<JsonRpcRequest, Box<dyn Error>> {
     // let mut buf_reader = BufReader::new(&mut socket);
     // let http_request: Vec<_> = buf_reader
     //     .by_ref()
@@ -70,7 +113,7 @@ fn read_request(mut socket: TcpStream) -> Result<JsonRpcRequest, Box<dyn Error>>
     }
 }
 
-fn read_payload(socket: TcpStream) -> Result<Vec<u8>, Box<dyn Error>> {
+fn read_payload(socket: &mut TcpStream) -> Result<Vec<u8>, Box<dyn Error>> {
     let mut reader = BufReader::new(socket);
     let mut length = 0;
     for result in reader.by_ref().lines() {
@@ -81,7 +124,7 @@ fn read_payload(socket: TcpStream) -> Result<Vec<u8>, Box<dyn Error>> {
 
         let header = "content-length: ";
         if l.to_lowercase().starts_with(header) {
-            length = usize::from_str_radix(&l[header.len()..], 10)?;
+            length = (&l[header.len()..]).parse::<usize>()?;
         }
     }
     let mut payload = vec![0u8; length];
@@ -89,3 +132,17 @@ fn read_payload(socket: TcpStream) -> Result<Vec<u8>, Box<dyn Error>> {
     reader.read_exact(payload.as_mut_slice())?;
     Ok(payload)
 }
+
+fn jsonrpc_result(id: JsonValue, result: impl Into<json::JsonValue>) -> String {
+    let payload = json::object! {
+        jsonrpc: "2.0",
+        id: id,
+        result: result.into(),
+    }
+    .dump();
+    format!(
+        "HTTP/1.1 200 OK\r\nContent-Length: {}\r\n\r\n{}",
+        payload.len(),
+        payload
+    )
+}
diff --git a/src/types/u256.rs b/src/types/u256.rs
index 662ea86..27f07ad 100644
--- a/src/types/u256.rs
+++ b/src/types/u256.rs
@@ -101,6 +101,7 @@ impl Display for U256 {
     }
 }
 
+#[cfg(test)]
 mod test {
     use super::U256;
     #[test]