Made it a library, as I should have done from the beginning

examples/demo3270.rs

@@ -0,0 +1,54 @@
+use structopt::StructOpt;
+use std::time::Duration;
+
+use tn3270s::tn3270;
+
+#[derive(StructOpt)]
+pub struct Cli {
+    #[structopt(short="h", long = "host", default_value="[::1]")]
+    host: String,
+    #[structopt(short="p", long = "port", default_value="2101")]
+    port: u16,
+
+}
+
+fn run(mut session: tn3270::Session) -> anyhow::Result<()> {
+    use tn3270::stream::*;
+    let mut record = WriteCommand::new(WriteCommandCode::Write, WCC::RESET);
+    let bufsz = BufferAddressCalculator { width: 80, height: 24 };
+    record.set_buffer_address(0)
+        .erase_unprotected_to_address(bufsz.encode_address(79, 23))
+        .set_buffer_address(bufsz.encode_address(31,1))
+        .set_attribute(ExtendedFieldAttribute::ForegroundColor(Color::Red))
+        .send_text("Hello from Rust!");
+    session.send_record(record)?;
+
+    std::thread::sleep(Duration::from_secs(60));
+    Ok(())
+}
+
+fn main() -> anyhow::Result<()> {
+    let options: Cli = Cli::from_args();
+    let server = std::net::TcpListener::bind((options.host.as_str(), options.port))?;
+
+    for client in server.incoming() {
+        let client = client?;
+        std::thread::spawn(move || {
+            let session = match tn3270::Session::new(client) {
+                Ok(session) => session,
+                Err(err) => {
+                    eprintln!("Error accepting session: {}", err);
+                    return;
+                }
+            };
+
+            if let Err(err) = run(session) {
+                eprintln!("Error in session: {}", err);
+            }
+
+        });
+    }
+    println!("Hello, world!");
+
+    Ok(())
+}