Source

`tests/purrc/app_netcat_test.cpp`

2// Original work; see ACKNOWLEDGMENTS.md for the open-source ideas we build upon.

3// System-level "application" test: a small TCP round-trip ("netcat"-style) app

4// that only passes if socket + string + io all cooperate end to end.

5//

6// This is deliberately a multi-module integration program, not a single-function

7// probe: it stands up a real loopback TCP connection, builds a message with the

8// `string` and `io` modules, ships it over the socket, reads it back on the peer

9// fd, and verifies byte-exactness -- all inside a SINGLE cheatah process.

10//

11// Why it doesn't deadlock in one process: for 127.0.0.1 the kernel completes the

12// TCP handshake on connect() and queues the connection on the listener's accept

13// backlog, so connect() returns before accept() is called and the subsequent

14// accept() returns immediately. The payload is small enough to fit in the socket

15// send buffer, so sendall() does not block waiting for a reader. Output is fully

16// deterministic (only booleans + fixed labels), so it can be asserted

17// byte-for-byte.

18//

19// Modules exercised: socket (tcp_listen/local_port/tcp_connect/accept/sendall/

20// recv/close), string (upper, concat), io (str, print), plus the builtin len().

22#include "e2e_harness.hpp"

25TEST(SystemApps, NetworkRoundtrip) {

26 e2e::expect_e2e("app_netcat", R"PURR(import io

27import string

28import socket

30let listener = socket.tcp_listen("127.0.0.1", 0, 8)

31let port = socket.local_port(listener)

32let client = socket.tcp_connect("127.0.0.1", port)

33let server = socket.accept(listener)

35let payload = string.upper("ping") + " " + io.str(port > 0)

36let sent = socket.sendall(client, payload)

37let got = socket.recv(server, 1024)

39io.print("listen_ok", listener >= 0)

40io.print("port_ok", port > 0)

41io.print("connect_ok", client >= 0)

42io.print("accept_ok", server >= 0)

43io.print("send_ok", sent == 0)

44io.print("len_match", len(got) == len(payload))

45io.print("bytes_match", got == payload)

47socket.close(server)

48socket.close(client)

49socket.close(listener)

50)PURR",

51 "listen_ok True\n"

52 "port_ok True\n"

53 "connect_ok True\n"

54 "accept_ok True\n"

55 "send_ok True\n"

56 "len_match True\n"

57 "bytes_match True\n");

58}