Modify client code to get it able to transmit data over I2P

README.md

@@ -16,7 +16,7 @@ When you send a message:
 ## Dependencies
 
 ```
- # apt install python3-pycryptodome
+ # apt install python3-pycryptodome python3-socks
 ```
 
 ## Contribution

ressenger_client.py

@@ -1,20 +1,124 @@
 #!/usr/bin/python3
+from __future__ import annotations
+import os
 import socket
 import struct
-import time
+import typing
 
-HOST = '127.0.0.1'
-PORT = 5273
+# Type alias for clarity
+Address = str
 
-def send_message(sock, data: bytes):
-    header = struct.pack('!I', len(data))
-    sock.sendall(header + data)
+# Default timeout for socket operations (seconds)
+_DEFAULT_TIMEOUT = 10.0
 
-if __name__ == '__main__':
-    with socket.create_connection((HOST, PORT)) as s:
-        send_message(s, b'hello binary \x00\x01')
-        time.sleep(0.2)
-        send_message(s, b'\xff'*1024)   # 发送 1KB 二进制
-        time.sleep(0.5)
-        send_message(s, b'last msg')
-        # 可关闭连接或继续发送更多消息
+
+def _prepare_payload(data: typing.Union[bytes, str]) -> bytes:
+    """
+    Convert data into bytes. If data is a str, encode with UTF-8.
+
+    Raises:
+        TypeError: if data is not bytes or str.
+    """
+    if isinstance(data, bytes):
+        return data
+    if isinstance(data, str):
+        return data.encode('utf-8')
+    raise TypeError("data must be bytes or str")
+
+
+def _pack_message(payload: bytes) -> bytes:
+    """
+    Prepend a 4-byte big-endian unsigned length to payload.
+    The protocol supports payload lengths up to 2**32 - 1 bytes.
+    """
+    length = len(payload)
+    if length >= (1 << 32):
+        raise ValueError("payload too large (must be less than 2**32 bytes)")
+    return struct.pack("!I", length) + payload
+
+
+def send_data(data: typing.Union[bytes, str], addr: Address, port: int) -> None:
+    """
+    Send a single length-prefixed message over plain TCP to (addr, port).
+
+    Parameters:
+      - data: bytes or str (if str, encoded as UTF-8)
+      - addr: IPv4/IPv6 address or hostname reachable directly
+      - port: TCP port on the destination
+
+    Behaviour:
+      - Connects, sends the framed message, then closes the socket.
+      - Raises built-in socket exceptions on failure.
+
+    Example:
+      send_data(b'hello', '192.0.2.1', 12345)
+    """
+    payload = _prepare_payload(data)
+    message = _pack_message(payload)
+
+    # Create a TCP connection with a timeout
+    with socket.create_connection((addr, port), timeout=_DEFAULT_TIMEOUT) as sock:
+        # Ensure blocking mode for sendall
+        sock.setblocking(True)
+        sock.sendall(message)
+
+
+def send_data_i2p(data: typing.Union[bytes, str], addr: Address, port: int) -> None:
+    """
+    Send a single length-prefixed message to an I2P destination via a local i2pd SOCKS5 proxy.
+
+    Parameters:
+      - data: bytes or str (if str, encoded as UTF-8)
+      - addr: I2P hostname, e.g. 'xxxxxxxxxxxxxx.b32.i2p' or 'mydest.i2p'
+      - port: destination port exposed by the I2P server tunnel
+
+    Behaviour:
+      - Uses PySocks (socks) to create a socket that speaks SOCKS5 to the local proxy.
+      - Uses remote DNS resolution (rdns=True) so that the proxy resolves .i2p names.
+      - Connects, sends the framed message, then closes the socket.
+      - Raises ImportError if PySocks is not installed.
+      - Raises socket or proxy-related exceptions on failure.
+
+    Environment variables:
+      - I2P_SOCKS_HOST (default '127.0.0.1')
+      - I2P_SOCKS_PORT (default '4447')
+
+    Example:
+      send_data_i2p(b'hello', 'abcd1234xxxxxxx.b32.i2p', 12345)
+    """
+    try:
+        import socks  # PySocks; license: MIT
+    except Exception as e:
+        raise ImportError(
+            "PySocks is required for send_data_i2p. "
+            "Install it with: pip install PySocks"
+        ) from e
+
+    payload = _prepare_payload(data)
+    message = _pack_message(payload)
+
+    socks_host = os.environ.get("I2P_SOCKS_HOST", "127.0.0.1")
+    socks_port_str = os.environ.get("I2P_SOCKS_PORT", "4447")
+    try:
+        socks_port = int(socks_port_str)
+    except ValueError:
+        raise ValueError("I2P_SOCKS_PORT environment variable must be an integer")
+
+    # Create a socksified socket. socks.socksocket has the same interface as socket.socket.
+    s = socks.socksocket()
+    # Use SOCKS5; rdns=True ensures the proxy resolves the .i2p name instead of local DNS.
+    s.set_proxy(proxy_type=socks.SOCKS5, addr=socks_host, port=socks_port, rdns=True)
+    s.settimeout(_DEFAULT_TIMEOUT)
+
+    try:
+        # Connect through the proxy to the I2P destination.
+        # When rdns=True, the proxy will perform name resolution for .i2p addresses.
+        s.connect((addr, port))
+        # Ensure blocking mode for sendall
+        s.setblocking(True)
+        s.sendall(message)
+    finally:
+        try:
+            s.close()
+        except Exception:
+            pass

ressenger_server.py

@@ -1,9 +1,5 @@
 #!/usr/bin/python3
-import socket
-import threading
-import struct
-import time
-import sys
+import socket, threading, struct, time, sys
 
 HOST = '0.0.0.0'