使用c语言，做一个简易netcat

使用C语言编写一个简易的Netcat（也称为nc）是一个基础的网络编程练习，通常涉及到套接字编程。这里给出一个简单的示例，演示如何创建一个基本的TCP客户端和服务端，用于接收和发送数据。由于实际的Netcat功能较为复杂，这个简化版仅实现了基本的数据转发。

**服务器端（server.c）:**

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

#define PORT 1234

int main() {
    int server_sock, client_sock;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(client_addr);

    // 创建服务器套接字
    server_sock = socket(AF_INET, SOCK_STREAM, 0);
    if (server_sock == -1) {
        perror("Error creating server socket");
        exit(1);
    }

    // 设置服务器地址和端口
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    // 绑定和监听
    if (bind(server_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("Error binding server");
        close(server_sock);
        exit(1);
    }
    listen(server_sock, 5);

    // 等待客户端连接
    printf("Server listening on port %d...\n", PORT);
    client_sock = accept(server_sock, (struct sockaddr *)&client_addr, &addr_len);
    if (client_sock == -1) {
        perror("Error accepting connection");
        exit(1);
    }

    // 读取客户端的数据并回发
    char buffer[1024];
    while (fgets(buffer, sizeof(buffer), stdin)) {
        send(client_sock, buffer, strlen(buffer), 0);
        printf("Echoing to client: %s\n", buffer);
    }

    // 关闭套接字
    close(client_sock);
    close(server_sock);

    return 0;
}

**客户端（client.c）:**

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 1234

int main() {
    int client_sock;
    struct sockaddr_in server_addr;
    char buffer[1024];

    // 创建客户端套接字
    client_sock = socket(AF_INET, SOCK_STREAM, 0);
    if (client_sock == -1) {
        perror("Error creating client socket");
        exit(1);
    }

    // 设置服务器地址和端口
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    inet_pton(AF_INET, SERVER_IP, &server_addr.sin_addr);

    // 连接到服务器
    if (connect(client_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("Error connecting to server");
        close(client_sock);
        exit(1);
    }

    // 发送数据到服务器
    printf("Enter message to send to the server>\n");
    fgets(buffer, sizeof(buffer), stdin);
    send(client_sock, buffer, strlen(buffer), 0);

    // 读取并打印服务器的响应
    read(client_sock, buffer, sizeof(buffer));
    printf("Response from server: %s\n", buffer);

    // 关闭套接字
    close(client_sock);

    return 0;
}

注意，这只是一个非常基础的Netcat实现，不具备反弹shell、加密等功能。如果你想实现更复杂的功能，需要深入理解网络编程原理并使用更专业的库，如libevent、openssl等。