Enumerate all of the listening processes and their ports

src/main.rs

@@ -0,0 +1,66 @@
+use procfs::process::FDTarget;
+use std::collections::HashMap;
+
+struct Entry {
+    port: u16,
+    desc: String,
+}
+
+fn get_entries() -> procfs::ProcResult<Vec<Entry>> {
+    let all_procs = procfs::process::all_processes()?;
+
+    // build up a map between socket inodes and process stat info. Ignore any
+    // error we encounter as it probably means we have no access to that
+    // process or something.
+    let mut map: HashMap<u64, String> = HashMap::new();
+    for p in all_procs {
+        if let Ok(process) = p {
+            if !process.is_alive() {
+                continue; // Ignore zombies.
+            }
+
+            if let (Ok(fds), Ok(cmd)) = (process.fd(), process.cmdline()) {
+                for fd in fds {
+                    if let Ok(fd) = fd {
+                        if let FDTarget::Socket(inode) = fd.target {
+                            map.insert(inode, cmd.join(" "));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    let mut h: HashMap<u16, Entry> = HashMap::new();
+
+    // Go through all the listening IPv4 and IPv6 sockets and take the first
+    // instance of listening on each port *if* the address is loopback or
+    // unspecified. (TODO: Do we want this restriction really?)
+    let tcp = procfs::net::tcp()?;
+    let tcp6 = procfs::net::tcp6()?;
+    for tcp_entry in tcp.into_iter().chain(tcp6) {
+        if tcp_entry.state == procfs::net::TcpState::Listen
+            && (tcp_entry.local_address.ip().is_loopback()
+                || tcp_entry.local_address.ip().is_unspecified())
+            && !h.contains_key(&tcp_entry.local_address.port())
+        {
+            if let Some(cmd) = map.get(&tcp_entry.inode) {
+                h.insert(
+                    tcp_entry.local_address.port(),
+                    Entry {
+                        port: tcp_entry.local_address.port(),
+                        desc: cmd.clone(),
+                    },
+                );
+            }
+        }
+    }
+
+    Ok(h.into_values().collect())
+}
+
+fn main() {
+    for e in get_entries().unwrap() {
+        println!("{}: {}", e.port, e.desc);
+    }
+}