diff --git a/.gitignore b/.gitignore
index 76caf3d8787fb5e33f2f07aca2397dcec249c003..e87145846b693ef6562677c879c86ecf8634cf6d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -53,3 +53,5 @@ examples/socket_server_2.gif
 examples/socket_server_2.dot
 examples/morse_key.wav
 examples/log_file_client.log
+examples/morse.wav
+examples/socket_client_2.dot
diff --git a/CHANGELOG b/CHANGELOG
index fb5277eda8d265142d1c013af5f0c7b4db881702..7f56c09848d13d7855ed58353126a9c299f88b71 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,12 +1,15 @@
 TODO::
   ? DSP::Clock_ptr => migrate to std::shared_ptr
-  update Linux makefile
   !!! Add TELEsound and PiAPS_sound projects to GitLab and start addaptation to new library version
 
   unsigned long SamplingRate // -1 => 0
 LAST DONE:
 
 CHANGES:
+- ver. 0.20.004 - <b>2021.04.06</b> Changed: 
+  - Fixed makefiles for Linux - install and examples compilation works
+  - Initial work on sockets support for Linux
+
 - ver. 0.20.003 - <b>2021.04.06</b> Changed: 
   - DSP::E_LS_Mode => DSP::e::LogState
   - DSP::LogMode => DSP::e::LogMode
diff --git a/src/cpp/DSP_sockets.cpp b/src/cpp/DSP_sockets.cpp
index 85edb4924ee7c92265df580daa6e068f5196c9ef..204ff9e985ab94c62c49dd8e8d5b204b468e4409 100644
--- a/src/cpp/DSP_sockets.cpp
+++ b/src/cpp/DSP_sockets.cpp
@@ -114,7 +114,7 @@ bool DSP::Socket::is_socket_error(const int &iResult) {
 
 int DSP::Socket::GetLastError() {
 #ifndef __NO_WINSOCK__
-  return WSAGetLastError());
+  return WSAGetLastError();
 #else
   return errno;
 #endif
@@ -264,7 +264,7 @@ bool DSP::Socket::TryAcceptConnection(void)
     return false;
   }
   //current_socket_state &= DSP::e::SocketStatus::timeout_mask; // no object
-  if (DSP::Socket::is_socket_valid(res) == true)
+  if (DSP::Socket::is_socket_error(res) == true)
   {
     DSP::log << "DSP::Socket::TryAcceptConnection" << DSP::e::LogMode::second << "SOCKET_ERROR" << endl;
     DSP::Socket::close_socket();
diff --git a/src/include/DSP_lib.h b/src/include/DSP_lib.h
index fa9cfd24fa220ebd52d24c95a896b4cd5fb44917..e6d13c603eadb5a1ea9684e7e610c5ee8d5d0135 100644
--- a/src/include/DSP_lib.h
+++ b/src/include/DSP_lib.h
@@ -11,7 +11,7 @@
 
 #define DSP_VER_MAJOR 0
 #define DSP_VER_MINOR 20
-#define DSP_VER_BUILD 3 // !!! without zeroes before, else this will be treated as octal number
+#define DSP_VER_BUILD 4 // !!! without zeroes before, else this will be treated as octal number
 #define DSP_VER_YEAR  2021
 #define DSP_VER       DSP_VER_MAJOR.DSP_VER_MINOR.DSP_VER_BUILD