init

three/messagerC.go

@@ -0,0 +1,118 @@
+// =============================================================================
+// Auth: Alex Celani
+// File: messagerC.go
+// Revn: 05-10-2022  0.3
+// Func:
+//
+// TODO: create
+// =============================================================================
+// CHANGE LOG
+// -----------------------------------------------------------------------------
+// 05-04-2022: init
+// 05-09-2022: began commenting
+// 05-10-2022: finished commenting
+//             added alter() and forward()
+//             made passed value to alter()/forward() a slice
+//             changed refs to recv byte array to slice of n bytes
+//
+// =============================================================================
+
+package main
+
+import ( 
+    "net"       // ResolveTCPAddr, conn.Write,Read,Close
+                // ListenTCP, listener.Accept
+    "os"        // Args, Stderr, Exit
+    "fmt"       // Fprintf, Println
+    "strings"   // ToLower
+)
+
+
+// quick error checking
+func check( err error ) {
+    // if user checks an error, it better be nil
+    if err != nil {
+        // put error in string, print in stderr
+        fmt.Fprintf( os.Stderr, "Fatal error: %s", err.Error() )
+        os.Exit( 2 )        // quit
+    }
+}
+
+
+// function to change received message before passing it along
+func alter( recv []byte ) string {
+    var send string = string( recv[:] )
+    send = send + " " + send
+    send = strings.ToLower( send )
+    return send
+}
+
+
+// function to convert message to string before forwarding
+func forward( recv []byte ) string {
+    return string( recv[:] )
+}
+
+
+// function to handle incoming connections
+func handleClient( conn net.Conn ) {
+    defer conn.Close()  // barring any error, still close connection
+
+    var buf [512]byte   // declare large byte array, store messages
+
+    // iterate forever to always read over connection
+    for {
+        // read n bytes from connection into buffer
+        n, err := conn.Read( buf[0:] )
+        if err != nil { // erroring on read will simply leave the 
+            return      // function so it can start again later
+        }
+
+        // print recv'd message
+        // string() only works on byte SLICES so [:] is required
+        fmt.Println( "recv: ", string( buf[:n] ) )
+
+        send := alter( buf[:n] )        // send message ot get changed
+//        send := forward( buf[:] )
+
+        // write that response back to original client
+        _, err = conn.Write( []byte( send ) )
+        if err != nil { // erroring on write will simply leave the
+            return      // function so it can start again later
+        }
+
+        fmt.Println( "sent: ", send )   // print response
+    }
+}
+
+
+func main() {
+
+    // ip:port
+    // ip doesn't exist, implies localhost
+    service := ":1202"      // capture ip address and host
+    
+    // "resolve" ip & host according to TCP rules
+    tcpAddr, err := net.ResolveTCPAddr( "tcp", service )
+    check( err )    // check error
+
+    // bind and "listen" to ip and port, according to tcp rules
+    listener, err := net.ListenTCP( "tcp", tcpAddr )
+    check( err )    // check error
+
+    // iterate forever
+    // TODO i mean i can totally make this more user friendly
+    for {
+        // accept a connection that makes its way to bound port
+        conn, err := listener.Accept()
+        if err != nil {     // if connection fails...
+            continue        // don't quit program, not fatal error
+        }
+
+        // asynchronous function to handle connection to client
+        go handleClient( conn )
+    }
+}
+
+
+