用C语言分别编写TCP客户端和客户端程序段 ，要求： 1. 已知服务器的域名，获取服务器IP地址，向服务器发出连接请求； 2. 连接成功后，发送客户端本地主机名和学生本人学号到服务器端。客户端接收回复数据，并进行判断。若回复包含“OK”，则客户端显示“登录成功”；否则，客户端显示“登录失败”。

好的，我可以为您提供一些参考代码，但请注意，以下代码仅供参考，具体实现可能需要根据您的具体需求进行调整。

TCP客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define PORT "12345" // 服务器端口号
#define MAXDATASIZE 100 // 最大数据长度

int main(int argc, char *argv[]) {
    int sockfd, numbytes;
    char buf[MAXDATASIZE];
    struct addrinfo hints, *servinfo, *p;
    int rv;
    char s[INET_ADDRSTRLEN];

    if (argc != 2) {
        fprintf(stderr,"usage: client hostname\n");
        exit(1);
    }

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
            perror("client: socket");
            continue;
        }

        if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("client: connect");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "client: failed to connect\n");
        return 2;
    }

    inet_ntop(p->ai_family, &(((struct sockaddr_in*)p->ai_addr)->sin_addr), s, sizeof s);
    printf("client: connecting to %s\n", s);

    freeaddrinfo(servinfo);

    // 发送数据
    char hostname[MAXDATASIZE];
    char student_id[MAXDATASIZE];
    printf("Please input hostname and student id:\n");
    scanf("%s%s", hostname, student_id);

    char send_data[MAXDATASIZE];
    strcpy(send_data, hostname);
    strcat(send_data, " ");
    strcat(send_data, student_id);
    if (send(sockfd, send_data, strlen(send_data), 0) == -1) {
        perror("send");
        close(sockfd);
        exit(1);
    }

    // 接收数据
    if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
        perror("recv");
        exit(1);
    }
    buf[numbytes] = '\0';
    printf("client: received '%s'\n",buf);

    // 判断登录是否成功
    if (strstr(buf, "OK") != NULL) {
        printf("Login succeeded!\n");
    } else {
        printf("Login failed!\n");
    }

    close(sockfd);

    return 0;
}

TCP服务器端代码：

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

#define PORT "12345" // 服务器端口号
#define BACKLOG 10 // 最大连接数
#define MAXDATASIZE 100 // 最大数据长度

void *get_in_addr(struct sockaddr *sa) {
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main() {
    int sockfd, new_fd;
    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_storage their_addr;
    socklen_t sin_size;
    char s[INET6_ADDRSTRLEN];
    int yes=1;
    char buf[MAXDATASIZE];
    int rv;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
            perror("server: socket");
            continue;
        }

        if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
            perror("setsockopt");
            exit(1);
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("server: bind");
            continue;
        }

        break;
    }

    freeaddrinfo(servinfo);

    if (p == NULL) {
        fprintf(stderr, "server: failed to bind\n");
        exit(1);
    }

    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }

    printf("server: waiting for connections...\n");

    while(1) {
        sin_size = sizeof their_addr;
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
        if (new_fd == -1) {
            perror("accept");
            continue;
        }

        inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s);
        printf("server: got connection from %s\n", s);

        if (!fork()) {
            close(sockfd);

            // 接收数据
            if (recv(new_fd, buf, MAXDATASIZE-1, 0) == -1) {
                perror("recv");
                exit(1);
            }
            buf[MAXDATASIZE-1] = '\0';
            printf("server: received '%s'\n", buf);

            // 判断登录是否成功
            if (strstr(buf, "localhost") != NULL && strstr(buf, "123456") != NULL) {
                if (send(new_fd, "OK", 2, 0) == -1) {
                    perror("send");
                }
            } else {
                if (send(new_fd, "FAIL", 4, 0) == -1) {
                    perror("send");
                }
            }

            close(new_fd);
            exit(0);
        }

        close(new_fd);
    }

    return 0;
}

这份代码实现了基本的需求，但仍有许多可以改进的地方，例如错误处理、输入校验等等。