如何配置和优化C语言编写的Telnet服务器端？

telnet 服务器端通常指的是运行 Telnet 服务的计算机，它允许客户端通过 Telnet 协议远程登录并进行命令行操作。

Telnet服务器端实现详解

Telnet是一种基于TCP/IP协议的远程登录协议，允许用户通过网络连接到另一台计算机并进行交互式操作，下面将详细介绍如何用C语言编写一个简单的Telnet服务器。

包含头文件

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

常量定义与全局变量

#define DEFAULTIP "127.0.0.1"
#define DEFAULTPORT 23
#define DEFAULTBACKLOG 5
#define MAXBUF 1024
#define MAXPATH 150
int main(int argc, char *argv[]);
void getoption(int argc, char **argv);
void prterrmsg(char *msg);
void wrterrmsg(char *msg);
void prtinfomsg(char *msg);
void wrtinfomsg(char *msg);
void AllocateMemory(char **s, int l, char *d);

错误处理函数

void prterrmsg(char *msg) {
    perror(msg);
    abort();
}
void wrterrmsg(char *msg) {
    fputs(msg, logfp);
    fputs(strerror(errno), logfp);
    fflush(logfp);
    abort();
}
void prtinfomsg(char *msg) {
    fputs(msg, stdout);
}
void wrtinfomsg(char *msg) {
    fputs(msg, logfp);
    fflush(logfp);
}

内存分配函数

void AllocateMemory(char **s, int l, char *d) {
    *s = malloc(l + 1);
    bzero(*s, l + 1);
    memcpy(*s, d, l);
}

命令行参数处理函数

void getoption(int argc, char **argv) {
    int c, len;
    char *p = NULL;
    opterr = 0;
    while (1) {
        int option_index = 0;
        static struct option long_options[] = {
            {"host", 1, 0, 'H'},
            {"port", 1, 0, 'P'},
            {"back", 1, 0, 'B'},
            {"dir", 1, 0, 'D'},
            {"log", 1, 0, 'L'},
            {"daemon", 0, 0, 'D'},
            {0, 0, 0, 0}
        };
        c = getopt_long(argc, argv, "H:P:B:D:L:D", long_options, &option_index);
        if (c == -1 || c == '?') break;
        if (optarg) len = strlen(optarg);
        else len = 0;
        switch (c) {
            case 'H': host = optarg; break;
            case 'P': port = optarg; break;
            case 'B': back = optarg; break;
            case 'D': dirroot = optarg; break;
            case 'L': logdir = optarg; break;
            case 'D': daemon_y_n = 1; break;
            default: prterrmsg("Unknown option"); break;
        }
    }
}

主函数

int main(int argc, char **argv) {
    // 初始化全局变量
    char *buffer = malloc(MAXBUF + 1);
    bzero(buffer, MAXBUF + 1);
    FILE *logfp = fopen(DEFAULTLOG, "a+");
    if (!logfp) {
        perror("Cannot open log file");
        return 1;
    }
    prtinfomsg("Starting Telnet server...
");
    getoption(argc, argv); // 解析命令行参数
    // 创建套接字
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        prterrmsg("Cannot create socket");
    }
    struct sockaddr_in server_addr;
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(host); // 默认使用本机地址
    server_addr.sin_port = htons(atoi(port)); // 默认使用23端口
    // 绑定套接字到指定IP和端口
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) {
        prterrmsg("Bind failed");
    }
    // 监听连接请求
    if (listen(sockfd, atoi(back))) {
        prterrmsg("Listen failed");
    }
    // 接受客户端连接并处理请求
    struct sockaddr_in client_addr;
    socklen_t client_len = sizeof(client_addr);
    int client_sock = accept(sockfd, (struct sockaddr *)&client_addr, &client_len);
    if (client_sock < 0) {
        prterrmsg("Accept failed");
    }
    prtinfomsg("Client connected!
");
    // 读写数据（简化示例）
    while (1) {
        int readbytes = recv(client_sock, buffer, MAXBUF, 0);
        if (readbytes <= 0) {
            wrterrmsg("Read error or connection closed by client");
            close(client_sock);
            break;
        }
        buffer[readbytes] = '