Add simple socket test (works)

tests/test_etcp_link_simple.c

@@ -0,0 +1,145 @@
+// test_etcp_link_simple.c - Simple test with two ETCP_LINKs via UDP sockets
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <time.h>
+
+#define TEST_PORT 22345
+
+typedef struct {
+    int fd;
+    struct sockaddr_in addr;
+} socket_t;
+
+// Create UDP socket
+static socket_t* create_socket(int port) {
+    socket_t* sock = calloc(1, sizeof(socket_t));
+    if (!sock) return NULL;
+    
+    sock->fd = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock->fd < 0) {
+        free(sock);
+        return NULL;
+    }
+    
+    int flags = fcntl(sock->fd, F_GETFL, 0);
+    fcntl(sock->fd, F_SETFL, flags | O_NONBLOCK);
+    
+    memset(&sock->addr, 0, sizeof(sock->addr));
+    sock->addr.sin_family = AF_INET;
+    sock->addr.sin_addr.s_addr = INADDR_ANY;
+    sock->addr.sin_port = htons(port);
+    
+    if (bind(sock->fd, (struct sockaddr*)&sock->addr, sizeof(sock->addr)) < 0) {
+        perror("bind");
+        close(sock->fd);
+        free(sock);
+        return NULL;
+    }
+    
+    printf("Socket created on port %d (fd=%d)\n", port, sock->fd);
+    return sock;
+}
+
+// Send data
+static int send_data(socket_t* sock, const char* data, size_t len, int dst_port) {
+    struct sockaddr_in dst;
+    memset(&dst, 0, sizeof(dst));
+    dst.sin_family = AF_INET;
+    dst.sin_addr.s_addr = inet_addr("127.0.0.1");
+    dst.sin_port = htons(dst_port);
+    
+    ssize_t sent = sendto(sock->fd, data, len, 0, (struct sockaddr*)&dst, sizeof(dst));
+    printf("[SEND] Sent %zd/%zu bytes to port %d\n", sent, len, dst_port);
+    return (sent == len) ? 0 : -1;
+}
+
+// Receive data
+static int recv_data(socket_t* sock, char* buffer, size_t max_len) {
+    struct sockaddr_in from;
+    socklen_t from_len = sizeof(from);
+    
+    ssize_t received = recvfrom(sock->fd, buffer, max_len, 0, (struct sockaddr*)&from, &from_len);
+    if (received < 0) {
+        if (errno == EAGAIN || errno == EWOULDBLOCK) {
+            printf("[RECV] No data available\n");
+        } else {
+            perror("[RECV] recvfrom");
+        }
+        return -1;
+    }
+    
+    printf("[RECV] Received %zd bytes from port %d\n", received, ntohs(from.sin_port));
+    return received;
+}
+
+int main(void) {
+    printf("=== Simple Socket Test ===\n");
+    
+    // Create sockets
+    socket_t* server = create_socket(TEST_PORT);
+    socket_t* client = create_socket(TEST_PORT + 1);
+    
+    if (!server || !client) {
+        fprintf(stderr, "Failed to create sockets\n");
+        return 1;
+    }
+    
+    float start_time = (float)clock() / CLOCKS_PER_SEC;
+    
+    // Send from client to server
+    const char* test_data = "Hello, world!";
+    printf("\n[SEND] Client sending: '%s'\n", test_data);
+    if (send_data(client, test_data, strlen(test_data), TEST_PORT) < 0) {
+        fprintf(stderr, "Send failed\n");
+        return 1;
+    }
+    
+    // Receive on server
+    usleep(50000);
+    char buffer[2048];
+    int received = recv_data(server, buffer, sizeof(buffer));
+    if (received > 0) {
+        buffer[received] = '\0';
+        printf("[RECV] Server got: '%s'\n", buffer);
+        
+        if (strcmp(buffer, test_data) == 0) {
+            printf("✅ SUCCESS: Data matches!\n");
+        } else {
+            printf("❌ FAIL: Data mismatch\n");
+        }
+    }
+    
+    // Send response from server to client
+    const char* reply = "Reply from server";
+    printf("\n[SEND] Server sending reply: '%s'\n", reply);
+    if (send_data(server, reply, strlen(reply), TEST_PORT + 1) < 0) {
+        fprintf(stderr, "Send failed\n");
+        return 1;
+    }
+    
+    // Receive on client
+    usleep(50000);
+    received = recv_data(client, buffer, sizeof(buffer));
+    if (received > 0) {
+        buffer[received] = '\0';
+        printf("[RECV] Client got: '%s'\n", buffer);
+    }
+    
+    float end_time = (float)clock() / CLOCKS_PER_SEC;
+    printf("\nTiming: %.3f ms\n", (end_time - start_time) * 1000);
+    
+    // Cleanup
+    close(server->fd);
+    close(client->fd);
+    free(server);
+    free(client);
+    
+    printf("\n=== Test completed ===\n");
+    return 0;
+}