Renaming

problem_00/.dockerignore

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+/target/

problem_00/.gitignore

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+/target/

problem_00/Cargo.toml

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+[package]
+name = "problem_00"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+env_logger = "0.9.0"
+log = "0.4.0"
+tokio = { version = "1.27.0", features = ["full"] }

problem_00/Dockerfile

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+FROM rust:latest as builder
+RUN apt-get update && apt-get -y install ca-certificates cmake musl-tools libssl-dev && rm -rf /var/lib/apt/lists/*
+COPY . .
+RUN rustup default stable && rustup update
+RUN rustup target add x86_64-unknown-linux-musl
+ENV PKG_CONFIG_ALLOW_CROSS=1
+RUN cargo build --target x86_64-unknown-linux-musl --release
+FROM scratch
+COPY --from=builder /target/x86_64-unknown-linux-musl/release/problem_00 .
+EXPOSE 8080
+CMD ["/problem_00"]

problem_00/fly.toml

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+# fly.toml app configuration file generated for restless-bush-123 on 2023-04-19T13:36:26+02:00
+#
+# See https://fly.io/docs/reference/configuration/ for information about how to use this file.
+#
+
+app = "restless-bush-123"
+primary_region = "ams"
+
+[experimental]
+  auto_rollback = true
+
+[env]
+  ECHO_PORT = "8080"
+
+[[services]]
+  protocol = "tcp"
+  internal_port = 8080
+
+  [[services.ports]]
+    port = 8080

problem_00/src/main.rs

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+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpListener;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    env_logger::init();
+    let listener = TcpListener::bind("0.0.0.0:8080").await?;
+    log::info!("Start TCP server");
+    loop {
+        let (mut socket, _) = listener.accept().await?;
+
+        tokio::spawn(async move {
+            let mut buf = [0; 1024];
+
+            loop {
+                let n = match socket.read(&mut buf).await {
+                    Ok(n) if n == 0 => {
+                        log::info!("Receiving echo: {}", n);
+                        return;
+                    }
+                    Ok(n) => {
+                        log::info!("Receiving echo: {}", n);
+                        n
+                    }
+                    Err(e) => {
+                        log::error!("failed to read from socket; err = {:?}", e);
+                        return;
+                    }
+                };
+
+                if let Err(e) = socket.write_all(&buf[0..n]).await {
+                    log::error!("failed to write to socket; err = {:?}", e);
+                    return;
+                }
+            }
+        });
+    }
+}