minor tweaks

ch4/UDPEchoClient.c

@@ -2,6 +2,7 @@
 #include <netdb.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <string.h>
 
 #include "Practical.h"
 #include "ch4_common.h"
@@ -14,7 +15,7 @@ int main(int argc, char **argv) {
     char *server = argv[1];
     char *echo_str = argv[2];
 
-    const size_t echo_str_len = sizeof(echo_str);
+    const size_t echo_str_len = strlen(echo_str);
     if (echo_str_len > MAXSTRINGLENGTH) {
         DieWithUserMessage(echo_str, "string too long");
     }
@@ -55,7 +56,7 @@ int main(int argc, char **argv) {
     );
     if (num_bytes < 0) {
         DieWithSystemMessage("sendto() failed");
-    } else if (num_bytes != echo_str_len) {
+    } else if ((size_t) num_bytes != echo_str_len) {
         DieWithUserMessage("sendto() error", "sent unexpected amount of bytes");
     }
 
@@ -72,7 +73,7 @@ int main(int argc, char **argv) {
     );
     if (num_bytes < 0) {
         DieWithSystemMessage("recvfrom() failed");
-    } else if (num_bytes != echo_str_len) {
+    } else if ((size_t) num_bytes != echo_str_len) {
         DieWithUserMessage("recvfrom() error", "received unexpected amount of bytes");
     }