Handle args for client: use port in cli or default PORT

src/client.c

@@ -10,29 +10,21 @@
 
 
 int main(int argc, char *argv[]) {
-    int sockid;
+    int sockid, server_port;
     struct sockaddr_in client_socket;
     struct hostent *host;
     pid_t listener_pid, sender_pid, changed_pid;
 
+    server_port = handle_args(argc, argv);
+
     /* Signal handling */
     signal(SIGPIPE, SIG_IGN);
     signal(SIGINT, interrupt);
     signal(SIGTERM, interrupt);
 
-    /* Make sure we only get one and ony one argument */
-    if (argc != 2) {
-        fprintf(stderr, "usage: %s <server_hostname|server_ip>\n", argv[0]);
-        return EXIT_FAILURE;
-    }
-
     /* Initialize default values for the socket */
     client_socket.sin_family = AF_INET;
-    #ifdef PORT
-    client_socket.sin_port = htons(PORT);
-    #else
-    client_socket.sin_port = 0;
-    #endif
+    client_socket.sin_port = htons(server_port);
     /* Get server address */
     if ((host = gethostbyname(argv[1])) == NULL) {
         fprintf(stderr, "gethostbyname: error %d\n", h_errno);
@@ -92,6 +84,28 @@ int main(int argc, char *argv[]) {
     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 == 2)
+        return PORT;
+
+    /* Command line has a port, convert it to int */
+    if (argc == 3) {
+        port = strtol(argv[2], 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_hostname|server_ip> [<server_port>]\n", argv[0]);
+    exit(EXIT_FAILURE);
+}
+
 /* Process that reads messages from the server and prints them to stdout */
 void Listener(int sockid) {
     char buf[BUF_LEN];

src/client.h

@@ -1,6 +1,9 @@
 #ifndef CLIENT_H
 #define CLIENT_H
 
+/* Handle command line arguments */
+int handle_args(int, char**);
+
 /* Process that reads messages from the server and prints them to stdout */
 void Listener(int);