Add server functionality to the emulated modem

emulator.pas

@@ -26,9 +26,9 @@ type
     //Modem connection state
     Connection = record
         Call: boolean;
+        Answer: boolean;
         Addr: longword;
         Port: word;
-        Answer: boolean;
         Hang: boolean;
     end;
     {$endif}
@@ -50,7 +50,7 @@ const
     {$endif}
 
 var
-    Hlt, Echo{$ifdef floppy}, DiscRead, DiscWrite, DiscTrackSet, DiscSectSet{$endif}{$ifdef modem}, Calling{$endif}: boolean; //Halt and echo flags, disc system flags, and modem connection flag
+    Hlt, Echo{$ifdef floppy}, DiscRead, DiscWrite, DiscTrackSet, DiscSectSet{$endif}{$ifdef modem}, Calling, Answering{$endif}: boolean; //Halt and echo flags, disc system flags, and modem connection flags
     Op, Regs: 0 .. $f; //Opcode
     X, Y: 0 .. 3; //Register arguments
     Addr, IP, RP: word; //Immediate or address argument and instruction and return pointers
@@ -78,8 +78,8 @@ var
     {$ifdef modem}
     ModemConn: Connection; //State of the modem
     ModemState: file of Connection; //File storing the state of the modem
-    ServerSocket: longint; //Server socket
+    ServerSocket, ListenSocket, ClientSocket, ClientAddrSize: longint; //Server socket
-    ServerAddr: TInetSockAddr; //Server address
+    ServerAddr, ClientAddr: TInetSockAddr; //Server address
     {$endif}
     {$ifdef status}
     FileDescs: TFDset; //File descriptor set
@@ -133,14 +133,40 @@ begin
         end;
     end;
     //Hang
-    if ModemConn.Hang then if Calling then begin
+    if ModemConn.Hang then begin
-        CloseSocket (ServerSocket);
+        if Calling then begin
-        ModemConn.Hang := false;
+            CloseSocket (ServerSocket);
-        Calling := false;
+            ModemConn.Hang := false;
+            Calling := false;
+        end
+        else if Answering then begin
+            CloseSocket (ClientSocket);
+            CloseSocket (ListenSocket);
+            ModemConn.Hang := false;
+            Answering := false;
+        end;
     end
-    else if ModemConn.Call then if Calling then begin
+    else if ModemConn.Call then begin
-        CloseSocket (ServerSocket);
+        if Calling then begin
-        Calling := false;
+            CloseSocket (ServerSocket);
+            Calling := false;
+        end
+        else if Answering then begin
+            CloseSocket (ClientSocket);
+            CloseSocket (ListenSocket);
+            Answering := false;
+        end;
+    end
+    else if ModemConn.Answer then begin
+        if Calling then begin
+            CloseSocket (ServerSocket);
+            Calling := false;
+        end
+        else if Answering then begin
+            CloseSocket (ClientSocket);
+            CloseSocket (ListenSocket);
+            Answering := false;
+        end;
     end;
     //Call
     if ModemConn.Call then if Calling = false then begin
@@ -149,14 +175,36 @@ begin
         if ServerSocket <> -1 then begin
             //Connect
             ServerAddr.sin_family := AF_INET;
-            ServerAddr.sin_port := htons (ModemConn.Port);
             ServerAddr.sin_addr.s_addr := htonl (ModemConn.Addr);
-            if fpconnect (ServerSocket, @ServerAddr, Sizeof (ServerAddr)) <> -1 then begin
+            ServerAddr.sin_port := htons (ModemConn.Port);
+            if fpConnect (ServerSocket, @ServerAddr, Sizeof (ServerAddr)) <> -1 then begin
                 ModemConn.Call := false;
                 Calling := true;
             end;
         end;
     end;
+    //Answer
+    if ModemConn.Answer then if Answering = false then begin
+        //Create a socket
+        ListenSocket := fpSocket (AF_INET, SOCK_STREAM, 0);
+        if ListenSocket <> -1 then begin
+            //Listen
+            ServerAddr.sin_family := AF_INET;
+            ServerAddr.sin_addr.s_addr := htonl (ModemConn.Addr);
+            ServerAddr.sin_port := htons (ModemConn.Port);
+            if fpBind (ListenSocket, @ServerAddr, Sizeof (ServerAddr)) <> -1 then begin            
+                if fpListen (ListenSocket, 1) <> -1 then begin
+                    //Accept
+                    ClientAddrSize := sizeof (ClientAddr);
+                    ClientSocket := fpAccept (ListenSocket, @ClientAddr, @ClientAddrSize) ;
+                    if ClientSocket <> -1 then begin
+                        ModemConn.Answer := false;
+                        Answering := true;
+                    end;
+                end;
+            end;
+        end;
+    end;
     //Save the modem state
     if FileExists (ExpandFileName ('~/.thingamajig/connection')) then begin
         try
@@ -261,12 +309,13 @@ begin
     //Modem
     else if W = $fffa then begin
         {$ifndef fast}
-        wait (26);
+        wait (33);
         {$endif}
         //Connect
         CallServer;
         //Recieve
         if Calling then fpRecv (ServerSocket, @B, 1, 0)
+        else if Answering then fpRecv (ClientSocket, @B, 1, 0)
         else B := 0;
     end
     {$endif}
@@ -299,6 +348,11 @@ begin
             fpfd_zero (FileDescs);
             fpfd_set (ServerSocket, FileDescs);
             if fpSelect (ServerSocket + 1, @FileDescs, nil, nil, 0) > 0 then B := B or $20;
+        end
+        else if Answering then begin
+            fpfd_zero (FileDescs);
+            fpfd_set (ClientSocket, FileDescs);
+            if fpSelect (ClientSocket + 1, @FileDescs, nil, nil, 0) > 0 then B := B or $20;
         end;
         {$endif}
         {$ifndef modem}
@@ -651,12 +705,13 @@ begin
     //Modem
     else if W = $fffa then begin
         {$ifndef fast}
-        wait (26);
+        wait (33);
         {$endif}
         //Connect
         CallServer;
         //Send
-        if Calling then fpSend (ServerSocket, @B, 1, 0);
+        if Calling then fpSend (ServerSocket, @B, 1, 0)
+        else if Answering then fpSend (ClientSocket, @B, 1, 0);
     end
     {$endif}
     //Regular store
@@ -877,7 +932,11 @@ begin
 
     {$ifdef modem}
     //Disconnect the modem
-    if Calling then CloseSocket (ServerSocket);
+    if Calling then CloseSocket (ServerSocket)
+    else if Answering then begin
+        CloseSocket (ClientSocket);
+        CloseSocket (ListenSocket);
+    end;
     {$endif}
 
     {$ifndef fast}

modemctl.pas

@@ -8,9 +8,9 @@ type
     //Connection state
     Connection = record
         Call: boolean;
+        Answer: boolean;
         Addr: longword;
         Port: word;
-        Answer: boolean;
         Hang: boolean;
     end;
 
@@ -23,14 +23,20 @@ begin
 
     //Check the arguments
     if ParamStr (1) = '-c' then begin
-        if ParamCount > 2 then begin
+        if ParamCount <> 2 then begin
-            writeln ('Usage: modemctl [-c address:port]/-a/-h');
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
+            halt (1);
+        end;
+    end
+    else if ParamStr (1) = '-a' then begin
+        if ParamCount <> 2 then begin
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
             halt (1);
         end;
     end
     else begin
         if ParamCount > 1 then begin
-            writeln ('Usage: modemctl [-c address:port]/-a/-h');
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
             halt (1);
         end;
     end;
@@ -38,59 +44,53 @@ begin
     //Assign the state file
     assign (State, ExpandFileName ('~/.thingamajig/connection'));
 
-    //Read existing state if any
-    if FileExists (ExpandFileName ('~/.thingamajig/connection')) then begin
-        try
-            reset (State);
-            read (State, ModemConn);
-            close (State);
-        except
-        end;
-    end
-    //Or else assign a default state
-    else begin
-        ModemConn.Call := false;
-        ModemConn.Addr := 0;
-        ModemConn.Port := 0;
-        ModemConn.Answer := false;
-        ModemConn.Hang := false;
-    end;
-
     //Set the connection
     if ParamStr (1) = '-c' then begin
         ModemConn.Call := true;
+        ModemConn.Answer := false;
         try
             Addr := StrToHostAddr (ExtractDelimited (1, ParamStr (2), [':']));
             ModemConn.Addr := Addr.s_addr;
         except
-            writeln ('Usage: modemctl [-c address:port]/-a/-h');
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
             halt (1);
         end;
         try
             ModemConn.Port := StrToInt (ExtractDelimited (2, ParamStr (2), [':']));
         except
-            writeln ('Usage: modemctl [-c address:port]/-a/-h');
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
             halt (1);
         end;
-        ModemConn.Answer := false;
         ModemConn.Hang := false;
     end
     else if ParamStr (1) = '-a' then begin
         ModemConn.Call := false;
-        ModemConn.Addr := 0;
-        ModemConn.Port := 0;
         ModemConn.Answer := true;
+        try
+            Addr := StrToHostAddr (ExtractDelimited (1, ParamStr (2), [':']));
+            ModemConn.Addr := Addr.s_addr;
+        except
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
+            halt (1);
+        end;
+        try
+            ModemConn.Port := StrToInt (ExtractDelimited (2, ParamStr (2), [':']));
+        except
+            writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
+            halt (1);
+        end;
+        ModemConn.Hang := false;
         ModemConn.Hang := false;
     end
     else if ParamStr (1) = '-h' then begin
         ModemConn.Call := false;
+        ModemConn.Answer := false;
         ModemConn.Addr := 0;
         ModemConn.Port := 0;
-        ModemConn.Answer := false;
         ModemConn.Hang := true;
     end        
     else begin
-        writeln ('Usage: modemctl [-c address:port]/-a/-h');
+        writeln ('Usage: modemctl [-c address:port]/[-a address:port]/-h');
         halt (1);
     end;
 

readme.md

@@ -98,7 +98,7 @@ Usage:
   * emulator (-v) program (2> verbose_output)
   * tapectl (-r tape) (-p tape)
   * floppyctl (-0 disc) (-1 disc)
-  * modemctl [-c address:port]/-a/-h
+  * modemctl [-c address:port]/[-a address:port]/-h
 
 By default the emulator runs at roughly 500 KIPS and has 2 KiB of RAM.
 The arguments -dRAM4, -dRAM8, -dRAM16, -dRAM32, and -dRAM64 can be used
@@ -133,10 +133,10 @@ arguments -0 and -1 respectively. The disc system uses hard sectored
 single-sided discs with 77 tracks of 32 sectors of 137 bytes, or 337568
 bytes in total: the disc files must be of this size. The modem is
 controlled by the program modemctl: the option -c is used to call an IP
-address and port, -a to set the modem ready for answering calls to port
+address and port, -a to set the modem ready for answering calls to a
-1337, and -h to hang. Hanging manually is not necessary when making a
+loopback or local IP address and port, and -h to hang. Hanging manually
-new call or switching between calling and answering. Note: Answering is
+is not necessary when making or answering a new call or switching
-not implemented yet.
+between calling and answering.
 
 The floppy disc system uses two ports: command at FFFB and data at FFFC.
 Only the low nibble of the command port is used, consisting of a