added ifdefs for info printouts

socket_examples/simple_server.c

+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/socket.h>
+#include <netinet/ip.h>
+#include <string.h>
+
+static int bind_server_socket(int fd, int port);
+
+/*
+ * create a server socket bound to port
+ * and listening.
+ *  
+ * return positive file descriptor 
+ * or negative value on error
+ */
+int create_server_socket(int port)
+{
+    int fd = -1;
+    
+    if(port < 0 || port > 65535) {
+       errno = EINVAL;
+       return -1;
+    }
+    fd = socket(AF_INET,SOCK_STREAM,0);
+    if(fd < 0) return fd;
+    if(bind_server_socket(fd,port) < 0) return -1;
+
+    if(listen(fd,10)) return -1;
+
+    return fd;
+}
+
+static int bind_server_socket(int fd, int port){
+
+    struct sockaddr_in addr;
+    int val = 1;
+    if(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val))) {
+        perror("setsockopt");
+        return -1;
+    }
+    
+    // see man page ip(7)
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+    addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+
+    if(bind(fd, (struct sockaddr*) &addr, sizeof(addr))) return -1;
+
+#ifdef INFO
+    printf("bound fd %d to port %d (%x)\n",fd,port,addr.sin_port);
+#endif
+    
+    return fd;
+}
+
+/*
+ * Serve one client: send a message and close the socket
+ */
+static int do_serve(int fd)
+{
+    struct sockaddr_in client;
+    socklen_t addrlen = sizeof(client);
+    int clientfd;
+    const char* msg = "Hello, socket!\n"
+                      "I am a text\n"
+                      "BYE.\n";
+    size_t len = strlen(msg);
+    
+    printf("attempting accept on fd %d\n",fd);
+    if((clientfd = accept(fd,(struct sockaddr*) &client, &addrlen)) < 0) return -1;
+#ifdef INFO
+    printf("writing msg (len=%lu) to clientfd %d (port %d)\n",len,clientfd,client.sin_port);
+#endif
+    
+#ifdef WRITE_LOOP
+    size_t written = 0;
+    do {
+        int res = write(clientfd, msg, len);
+        if (res < 0) {
+            perror("write to clientfd");
+            goto error;
+        }
+#ifdef INFO
+        printf("write returned %d\n",res);
+#endif
+        written += res;
+    } while (written < len);
+#else
+    int res = write(clientfd, msg, len);
+    if (res < 0) {
+        perror("write to clientfd");
+        goto error;
+    }
+#endif
+
+ error:
+    printf("closing clientfd\n");
+    return close(clientfd);
+}
+
+int main()
+{
+    int fd = create_server_socket(5000);
+
+    if(fd < 0){
+        perror("create_server_socket");
+        return 1;
+    }
+
+    do_serve(fd);
+
+    printf("closing socket: %d\n", fd);
+    close(fd);
+
+    return 0;
+}