net: rename Sock::Reset() to Sock::Close() and make it private

Outside of `Sock`, `Sock::Reset()` was used in just one place (in
`i2p.cpp`) which can use the assignment operator instead.

This simplifies the public `Sock` API by having one method less.

src/util/sock.cpp

@@ -39,11 +39,11 @@ Sock::Sock(Sock&& other)
     other.m_socket = INVALID_SOCKET;
 }
 
-Sock::~Sock() { Reset(); }
+Sock::~Sock() { Close(); }
 
 Sock& Sock::operator=(Sock&& other)
 {
-    Reset();
+    Close();
     m_socket = other.m_socket;
     other.m_socket = INVALID_SOCKET;
     return *this;
@@ -51,21 +51,6 @@ Sock& Sock::operator=(Sock&& other)
 
 SOCKET Sock::Get() const { return m_socket; }
 
-void Sock::Reset() {
-    if (m_socket == INVALID_SOCKET) {
-        return;
-    }
-#ifdef WIN32
-    int ret = closesocket(m_socket);
-#else
-    int ret = close(m_socket);
-#endif
-    if (ret) {
-        LogPrintf("Error closing socket %d: %s\n", m_socket, NetworkErrorString(WSAGetLastError()));
-    }
-    m_socket = INVALID_SOCKET;
-}
-
 ssize_t Sock::Send(const void* data, size_t len, int flags) const
 {
     return send(m_socket, static_cast<const char*>(data), len, flags);
@@ -372,6 +357,22 @@ bool Sock::IsConnected(std::string& errmsg) const
     }
 }
 
+void Sock::Close()
+{
+    if (m_socket == INVALID_SOCKET) {
+        return;
+    }
+#ifdef WIN32
+    int ret = closesocket(m_socket);
+#else
+    int ret = close(m_socket);
+#endif
+    if (ret) {
+        LogPrintf("Error closing socket %d: %s\n", m_socket, NetworkErrorString(WSAGetLastError()));
+    }
+    m_socket = INVALID_SOCKET;
+}
+
 #ifdef WIN32
 std::string NetworkErrorString(int err)
 {

src/util/sock.h

@@ -68,11 +68,6 @@ public:
      */
     [[nodiscard]] virtual SOCKET Get() const;
 
-    /**
-     * Close if non-empty.
-     */
-    virtual void Reset();
-
     /**
      * send(2) wrapper. Equivalent to `send(this->Get(), data, len, flags);`. Code that uses this
      * wrapper can be unit tested if this method is overridden by a mock Sock implementation.
@@ -245,6 +240,12 @@ protected:
      * Contained socket. `INVALID_SOCKET` designates the object is empty.
      */
     SOCKET m_socket;
+
+private:
+    /**
+     * Close `m_socket` if it is not `INVALID_SOCKET`.
+     */
+    void Close();
 };
 
 /** Return readable error string for a network error code */