c unixsocket

~/C/unixsocket/client.c

@@ -0,0 +1,79 @@
+// https://systemprogrammingatntu.github.io/mp2/unix_socket.html
+
+#define SOCKET_NAME "/tmp/resol.sock"
+#define BUFFER_SIZE 12
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[]) {
+    struct sockaddr_un addr;
+    int i;
+    int ret;
+    int data_socket;
+    char buffer[BUFFER_SIZE];
+
+    /* Create local socket. */
+    data_socket = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (data_socket == -1) {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    /*
+     * For portability clear the whole structure, since some
+     * implementations have additional (nonstandard) fields in
+     * the structure.
+     */
+    memset(&addr, 0, sizeof(struct sockaddr_un));
+
+    /* Connect socket to socket address */
+    addr.sun_family = AF_UNIX;
+    strncpy(addr.sun_path, SOCKET_NAME, sizeof(addr.sun_path) - 1);
+
+    ret = connect (data_socket, (const struct sockaddr *) &addr,
+                   sizeof(struct sockaddr_un));
+    if (ret == -1) {
+        fprintf(stderr, "The server is down.\n");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Send arguments. */
+    for (i = 1; i < argc; ++i) {
+        ret = write(data_socket, argv[i], strlen(argv[i]) + 1);
+        if (ret == -1) {
+            perror("write");
+            break;
+        }
+    }
+
+    /* Request result. */
+    strcpy (buffer, "END");
+    ret = write(data_socket, buffer, strlen(buffer) + 1);
+    if (ret == -1) {
+        perror("write");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Receive result. */
+    ret = read(data_socket, buffer, BUFFER_SIZE);
+    if (ret == -1) {
+        perror("read");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Ensure buffer is 0-terminated. */
+    buffer[BUFFER_SIZE - 1] = 0;
+
+    printf("Result = %s\n", buffer);
+
+    /* Close socket. */
+    close(data_socket);
+
+    exit(EXIT_SUCCESS);
+}

~/C/unixsocket/server.c

@@ -0,0 +1,123 @@
+// https://systemprogrammingatntu.github.io/mp2/unix_socket.html
+
+#define SOCKET_NAME "/tmp/resol.sock"
+#define BUFFER_SIZE 12
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[]) {
+    struct sockaddr_un addr;
+    int down_flag = 0;
+    int ret;
+    int listen_socket;
+    int data_socket;
+    int result;
+    char buffer[BUFFER_SIZE];
+
+    /*
+     * In case the program exited inadvertently on the last run,
+     * remove the socket.
+     */
+    unlink(SOCKET_NAME);
+
+    /* Create local socket. */
+    listen_socket = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (listen_socket == -1) {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    /*
+     * For portability clear the whole structure, since some
+     * implementations have additional (nonstandard) fields in
+     * the structure.
+     */
+    memset(&addr, 0, sizeof(struct sockaddr_un));
+
+    /* Bind socket to socket name. */
+    addr.sun_family = AF_UNIX;
+    strncpy(addr.sun_path, SOCKET_NAME, sizeof(addr.sun_path) - 1);
+
+    ret = bind(listen_socket, (const struct sockaddr *) &addr,
+               sizeof(struct sockaddr_un));
+    if (ret == -1) {
+        perror("bind");
+        exit(EXIT_FAILURE);
+    }
+
+    /*
+     * Prepare for accepting connections. The backlog size is set
+     * to 20. So while one request is being processed other requests
+     * can be waiting.
+     */
+    ret = listen(listen_socket, 20);
+    if (ret == -1) {
+        perror("listen");
+        exit(EXIT_FAILURE);
+    }
+
+    /* This is the main loop for handling connections. */
+    for (;;) {
+        /* Wait for incoming connection. */
+        data_socket = accept(listen_socket, NULL, NULL);
+        if (data_socket == -1) {
+            perror("accept");
+            exit(EXIT_FAILURE);
+        }
+
+        result = 0;
+        for(;;) {
+            /* Wait for next data packet. */
+            ret = read(data_socket, buffer, BUFFER_SIZE);
+            if (ret == -1) {
+                perror("read");
+                exit(EXIT_FAILURE);
+            }
+
+            /* Ensure buffer is 0-terminated. */
+            buffer[BUFFER_SIZE - 1] = 0;
+
+            /* Handle commands. */
+            if (!strncmp(buffer, "DOWN", BUFFER_SIZE)) {
+                down_flag = 1;
+                break;
+            }
+
+            if (!strncmp(buffer, "END", BUFFER_SIZE)) {
+                break;
+            }
+
+            /* Add received summand. */
+            result += atoi(buffer);
+        }
+
+        /* Send result. */
+        sprintf(buffer, "%d", result);
+        ret = write(data_socket, buffer, BUFFER_SIZE);
+
+        if (ret == -1) {
+            perror("write");
+            exit(EXIT_FAILURE);
+        }
+
+        /* Close socket. */
+        close(data_socket);
+
+        /* Quit on DOWN command. */
+        if (down_flag) {
+            break;
+        }
+    }
+
+    close(listen_socket);
+
+    /* Unlink the socket. */
+    unlink(SOCKET_NAME);
+
+    exit(EXIT_SUCCESS);
+}