Handle args for server: use port in cli, PORT #ifdef, #else 0

src/server.c

@@ -16,9 +16,8 @@
  * */
 struct client_details clients[MAX_CLIENTS];
 
-int main(void) {
-    int serv_sockid, client_sockid;
-    int client_id;
+int main(int argc, char *argv[]) {
+    int server_port, serv_sockid, client_sockid, client_id;
     int message_pipe[2];
     struct sockaddr_in server_socket;
     struct sockaddr_in client_socket;
@@ -28,6 +27,8 @@ int main(void) {
     long addr_len;
     char eot = EOT;
 
+    server_port = handle_args(argc, argv);
+
     /* Signal handling */
     signal(SIGCHLD, interrupt);
     signal(SIGINT, interrupt);
@@ -43,11 +44,7 @@ int main(void) {
 
     /* Initialize default values for the socket */
     server_socket.sin_family = AF_INET;
-    #ifdef PORT
-    server_socket.sin_port = htons(PORT);
-    #else
-    server_socket.sin_port = 0;
-    #endif
+    server_socket.sin_port = htons(server_port);
     #ifdef LISTEN_ALL
     server_socket.sin_addr.s_addr = makeip4(0, 0, 0, 0);
     #else
@@ -133,6 +130,33 @@ int main(void) {
     return EXIT_SUCCESS;
 }
 
+/* Handle command line arguments */
+int handle_args(int argc, char *argv[]) {
+    long port;
+
+    /* Command line has no port, use default */
+    if (argc == 1) {
+        #ifdef PORT
+            return PORT;
+        #else
+            return 0;
+        #endif
+    }
+
+    /* Command line has a port, convert it to int */
+    if (argc == 2) {
+        port = strtol(argv[1], NULL, 10);
+        if ((0 < port) && (port < 65536)) {
+            // Conversion OK, return the port
+            return (int) port;
+        }
+        // Otherwise, could not convert: exit down below
+    }
+
+    fprintf(stderr, "usage: %s [<server_port>]\n", argv[0]);
+    exit(EXIT_FAILURE);
+}
+
 /* Compute the next free client_id in the client array */
 int get_next_free_client_id(void) {
     for (int i = 0; i < MAX_CLIENTS; i++) {

src/server.h

@@ -10,6 +10,9 @@ struct client_details {
     int pipe[2];
 };
 
+/* Handle command line arguments */
+int handle_args(int, char**);
+
 /* Compute the next free client_id in the client array */
 int get_next_free_client_id(void);