if (argc != 2) { fputs("usage: ./client message\n", stderr); exit(1); }

这段代码的作用是判断命令行参数的个数是否等于2，如果不是则输出错误信息并退出程序。其中，argc是main函数的参数之一，代表命令行参数的个数。如果argc不等于2，代表命令行参数的个数不符合要求，此时程序需要输出使用说明并退出。

具体来说，这段代码会输出一条错误信息到标准错误流(stderr)，提示用户正确的用法，即输入命令"./client message"，其中message代表用户想要发送的消息。然后调用exit函数，结束程序的执行。

相关问题

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <netinet/in.h> #define MAXLINE 80 #define SERV_PORT 6666 int main(int argc, char *argv[]) { struct sockaddr_in servaddr; char buf[MAXLINE]; int sockfd, n; char *str; if (argc != 2) { fputs("usage: ./client message\n", stderr); exit(1); } str = argv[1]; sockfd = socket(AF_INET, SOCK_STREAM, 0); bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family = AF_INET; inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr); servaddr.sin_port = htons(SERV_PORT); connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)); write(sockfd, str, strlen(str)); n = read(sockfd, buf, MAXLINE); printf("Response from server:\n"); write(STDOUT_FILENO, buf, n); close(sockfd); return 0; }如何运行这个ke'hukehu端

要运行这个客户端程序，您需要先将其保存为一个 C 语言源文件（例如 client.c），然后使用 C 编译器将其编译为可执行文件。

假设您使用的是 GCC 编译器，可以在终端中使用以下命令编译客户端程序：

gcc -o client client.c

该命令将编译 client.c 文件并生成一个名为 client 的可执行文件。

接下来，您可以使用以下命令运行客户端程序：

./client message

其中，message 是您要发送给服务器的字符串消息。请确保服务器正在运行并且监听相应的端口，以便客户端可以成功连接到服务器。

帮我用c++写windows下基于socket通信的聊天室服务器与客户端实现的代码 完成功能： 1.用户注册功能； 2.两个用户服务器发送私密消息； 3.用户创建一个或多个聊天群组； 4.用户加入群组、在群组内发送消息、离开群组； 5.用户之间的聊天信息通过服务器端转发；

以下是基于socket通信的聊天室服务器与客户端的代码，实现了功能：用户注册、私密消息发送、创建聊天群组、加入群组、在群组内发送消息、离开群组、用户之间的聊天信息通过服务器端转发。

服务器端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>

#pragma comment (lib, "ws2_32.lib")  //加载 ws2_32.dll

#define BUF_SIZE 100
#define MAX_CLNT 256

void ErrorHandling(char *message);

typedef struct {
    SOCKET socket;
    struct sockaddr_in addr;
    char name[20];
} client;

typedef struct {
    int count;
    client *clnt[MAX_CLNT];
} client_list;

client_list clnt_list = {0};

void send_message(char *message, int len, int sender, int receiver);
void send_message_all(char *message, int len, int sender);

int main(int argc, char *argv[]) {
    WSADATA wsaData;
    SOCKET serv_sock, clnt_sock;
    SOCKADDR_IN serv_addr, clnt_addr;
    int clnt_addr_size;
    char message[BUF_SIZE];
    int str_len, i;

    if (argc != 2) {
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        ErrorHandling("WSAStartup() error!");
    }

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if (serv_sock == INVALID_SOCKET) {
        ErrorHandling("socket() error!");
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    if (bind(serv_sock, (SOCKADDR*)&serv_addr, sizeof(serv_addr)) == SOCKET_ERROR) {
        ErrorHandling("bind() error!");
    }

    if (listen(serv_sock, MAX_CLNT) == SOCKET_ERROR) {
        ErrorHandling("listen() error!");
    }

    while (1) {
        clnt_addr_size = sizeof(clnt_addr);
        clnt_sock = accept(serv_sock, (SOCKADDR*)&clnt_addr, &clnt_addr_size);
        if (clnt_sock == INVALID_SOCKET) {
            continue;
        }

        client *new_client = (client*)malloc(sizeof(client));
        new_client->socket = clnt_sock;
        new_client->addr = clnt_addr;
        memset(new_client->name, 0, sizeof(new_client->name));
        clnt_list.clnt[clnt_list.count++] = new_client;
        printf("new client connected, count=%d\n", clnt_list.count);
        send_message_all("[Server] A new client connected.\n", 35, -1);

        while ((str_len = recv(clnt_sock, message, BUF_SIZE, 0)) != 0) {
            int index = -1;
            for (i = 0; i < clnt_list.count; i++) {
                if (clnt_list.clnt[i]->socket == clnt_sock) {
                    index = i;
                    break;
                }
            }
            if (index == -1) {
                break;
            }

            message[str_len] = '\0';
            if (strlen(message) == 0) {
                continue;
            }

            if (message[0] == '/') {
                char command[BUF_SIZE];
                int j = 1;
                while (j < str_len && message[j] != ' ') {
                    command[j - 1] = message[j];
                    j++;
                }
                command[j - 1] = '\0';

                if (strcmp(command, "name") == 0) {
                    char name[BUF_SIZE];
                    int k = j + 1;
                    while (k < str_len) {
                        name[k - j - 1] = message[k];
                        k++;
                    }
                    name[k - j - 1] = '\0';
                    strcpy(clnt_list.clnt[index]->name, name);
                    printf("client %s set name to %s\n", inet_ntoa(clnt_list.clnt[index]->addr.sin_addr), name);
                    send_message_all("[Server] A client set name.\n", 32, -1);
                } else if (strcmp(command, "to") == 0) {
                    char name[BUF_SIZE];
                    int k = j + 1;
                    while (k < str_len && message[k] != ' ') {
                        name[k - j - 1] = message[k];
                        k++;
                    }
                    name[k - j - 1] = '\0';
                    int receiver = -1;
                    for (i = 0; i < clnt_list.count; i++) {
                        if (strcmp(clnt_list.clnt[i]->name, name) == 0) {
                            receiver = i;
                            break;
                        }
                    }
                    if (receiver == -1) {
                        send_message("[Server] The client does not exist.\n", 38, -1, index);
                    } else {
                        send_message(message, str_len, index, receiver);
                    }
                } else if (strcmp(command, "create") == 0) {
                    char name[BUF_SIZE];
                    int k = j + 1;
                    while (k < str_len) {
                        name[k - j - 1] = message[k];
                        k++;
                    }
                    name[k - j - 1] = '\0';
                    int flag = 0;
                    for (i = 0; i < clnt_list.count; i++) {
                        if (strcmp(clnt_list.clnt[i]->name, name) == 0) {
                            flag = 1;
                            break;
                        }
                    }
                    if (flag == 1) {
                        send_message("[Server] The group name already exists.\n", 44, -1, index);
                    } else {
                        client *new_client = (client*)malloc(sizeof(client));
                        new_client->socket = -2;
                        memset(new_client->name, 0, sizeof(new_client->name));
                        clnt_list.clnt[clnt_list.count++] = new_client;
                        strcpy(clnt_list.clnt[clnt_list.count - 1]->name, name);
                        printf("client %s create group %s\n", inet_ntoa(clnt_list.clnt[index]->addr.sin_addr), name);
                        send_message_all("[Server] A client create group.\n", 34, -1);
                        send_message("[Server] The group created successfully.\n", 44, -1, index);
                    }
                } else if (strcmp(command, "join") == 0) {
                    char name[BUF_SIZE];
                    int k = j + 1;
                    while (k < str_len) {
                        name[k - j - 1] = message[k];
                        k++;
                    }
                    name[k - j - 1] = '\0';
                    int group = -1;
                    for (i = 0; i < clnt_list.count; i++) {
                        if (strcmp(clnt_list.clnt[i]->name, name) == 0 && clnt_list.clnt[i]->socket == -2) {
                            group = i;
                            break;
                        }
                    }
                    if (group == -1) {
                        send_message("[Server] The group does not exist.\n", 38, -1, index);
                    } else {
                        clnt_list.clnt[index]->socket = -3;
                        send_message("[Server] You have joined the group.\n", 38, -1, index);
                        send_message_all("[Server] A client joined the group.\n", 36, -1);
                        send_message("[Server] You can now send messages in the group.\n", 53, -1, index);
                    }
                } else if (strcmp(command, "leave") == 0) {
                    if (clnt_list.clnt[index]->socket != -3) {
                        send_message("[Server] You are not in a group.\n", 35, -1, index);
                    } else {
                        clnt_list.clnt[index]->socket = clnt_sock;
                        send_message("[Server] You left the group.\n", 32, -1, index);
                        send_message_all("[Server] A client left the group.\n", 35, -1);
                    }
                } else if (strcmp(command, "list") == 0) {
                    char list[BUF_SIZE];
                    memset(list, 0, sizeof(list));
                    for (i = 0; i < clnt_list.count; i++) {
                        if (clnt_list.clnt[i]->socket == -2) {
                            strcat(list, clnt_list.clnt[i]->name);
                            strcat(list, " ");
                        }
                    }
                    strcat(list, "\n");
                    send_message(list, strlen(list), -1, index);
                } else if (strcmp(command, "members") == 0) {
                    if (clnt_list.clnt[index]->socket != -3) {
                        send_message("[Server] You are not in a group.\n", 35, -1, index);
                    } else {
                        char members[BUF_SIZE];
                        memset(members, 0, sizeof(members));
                        for (i = 0; i < clnt_list.count; i++) {
                            if (clnt_list.clnt[i]->socket == -3) {
                                strcat(members, clnt_list.clnt[i]->name);
                                strcat(members, " ");
                            }
                        }
                        strcat(members, "\n");
                        send_message(members, strlen(members), -1, index);
                    }
                } else {
                    send_message("[Server] Invalid command.\n", 28, -1, index);
                }
            } else {
                if (clnt_list.clnt[index]->socket == -3) {
                    send_message_all(message, str_len, index);
                } else {
                    send_message_all(message, str_len, index);
                }
            }
        }

        for (i = 0; i < clnt_list.count; i++) {
            if (clnt_list.clnt[i]->socket == clnt_sock) {
                printf("client %s disconnected\n", inet_ntoa(clnt_list.clnt[i]->addr.sin_addr));
                send_message_all("[Server] A client disconnected.\n", 36, -1);
                int j;
                for (j = i; j < clnt_list.count - 1; j++) {
                    clnt_list.clnt[j] = clnt_list.clnt[j + 1];
                }
                clnt_list.count--;
                break;
            }
        }
        closesocket(clnt_sock);
    }

    closesocket(serv_sock);
    WSACleanup();
    return 0;
}

void ErrorHandling(char *message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

void send_message(char *message, int len, int sender, int receiver) {
    if (receiver < 0 || receiver >= clnt_list.count) {
        return;
    }
    send(clnt_list.clnt[receiver]->socket, message, len, 0);
    if (sender >= 0 && sender < clnt_list.count) {
        printf("client %s send message to %s: %s", inet_ntoa(clnt_list.clnt[sender]->addr.sin_addr), inet_ntoa(clnt_list.clnt[receiver]->addr.sin_addr), message);
    }
}

void send_message_all(char *message, int len, int sender) {
    int i;
    for (i = 0; i < clnt_list.count; i++) {
        if (sender == i) {
            continue;
        }
        send(clnt_list.clnt[i]->socket, message, len, 0);
    }
    if (sender >= 0 && sender < clnt_list.count) {
        printf("client %s send message to all: %s", inet_ntoa(clnt_list.clnt[sender]->addr.sin_addr), message);
    }
}

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>
#include <windows.h>
#include <conio.h>

#pragma comment (lib, "ws2_32.lib")  //加载 ws2_32.dll

#define BUF_SIZE 100

void ErrorHandling(char *message);
void menu();
void register_user(SOCKET hSocket);
void set_name(SOCKET hSocket);
void send_message(SOCKET hSocket);
void send_private_message(SOCKET hSocket);
void create_group(SOCKET hSocket);
void join_group(SOCKET hSocket);
void leave_group(SOCKET hSocket);
void list_group(SOCKET hSocket);
void list_members(SOCKET hSocket);

int main(int argc, char *argv[]) {
    WSADATA wsaData;
    SOCKET hSocket;
    SOCKADDR_IN serv_addr;
    char message[BUF_SIZE];
    int str_len;

    if (argc != 3) {
        printf("Usage : %s <IP> <port>\n", argv[0]);
        exit(1);
    }

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        ErrorHandling("WSAStartup() error!");
    }

    hSocket = socket(PF_INET, SOCK_STREAM, 0);
    if (hSocket == INVALID_SOCKET) {
        ErrorHandling("socket() error!");
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_addr.sin_port = htons(atoi(argv[2]));

    if (connect(hSocket, (SOCKADDR*)&serv_addr, sizeof(serv_addr)) == SOCKET_ERROR) {
        ErrorHandling("connect() error!");
    }

    menu();
    while (1) {
        char choice = getch();
        switch (choice) {
            case '1':
                register_user(hSocket);
                break;
            case '2':
                set_name(hSocket);
                break;
            case '3':
                send_message(hSocket);
                break;
            case '4':
                send_private_message(hSocket);
                break;
            case '5':
                create_group(hSocket);
                break;
            case '6':
                join_group(hSocket);
                break;
            case '7':
                leave_group(hSocket);
                break;
            case '8':
                list_group(hSocket);
                break;
            case '9':
                list_members(hSocket);
                break;
            case '0':
                closesocket(hSocket);
                WSACleanup();
                return 0;
            default:
                printf("Invalid choice.\n");
                break;
        }
        menu();
    }

    closesocket(hSocket);
    WSACleanup();
    return 0;
}

void ErrorHandling(char *message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

void menu() {
    system("cls");
    printf("=========================================\n");
    printf("1. Register\n");
    printf("2. Set name\n");
    printf("3. Send message to all\n");
    printf("4. Send private message\n");
    printf("5. Create group\n");
    printf("6. Join group\n");
    printf("7. Leave group\n");
    printf("8. List groups\n");
    printf("9. List members\n");
    printf("0. Exit\n");
    printf("=========================================\n");
}

void register_user(SOCKET hSocket) {
    char message[BUF_SIZE];
    printf("Enter username (max 19 characters): ");
    fgets(message, BUF_SIZE, stdin);
    message[strlen(message) - 1] = '\0';
    send(hSocket, message, strlen(message), 0);
    recv(hSocket, message, BUF_SIZE, 0);
    printf("%s\n", message);
}

void set_name(SOCKET hSocket) {
    char message[BUF_SIZE];
    printf("Enter your name (max 19 characters): ");
    fgets(message, BUF_SIZE, stdin);
    message[strlen(message) - 1] = '\0';
    sprintf(message, "/name %s", message);
    send(hSocket, message, strlen(message), 0);
}

void send_message(SOCKET hSocket) {
    char message[BUF_SIZE];
    printf("Enter message: ");
    fgets(message, BUF_SIZE, stdin);
    send(hSocket, message, strlen(message), 0);
}

void send_private_message(SOCKET hSocket) {
    char name[20], message[BUF_SIZE];
    printf("Enter receiver's name (max 19 characters): ");
    fgets(name, 20, stdin);
    name[strlen(name) - 1] = '\0';
    printf("Enter message: ");
    fgets(message, BUF_SIZE, stdin);
    sprintf(message, "/to %s %s", name, message);
    send(hSocket, message, strlen(message), 0);
}

void create_group(SOCKET hSocket) {
    char name[20], message[BUF_SIZE];
    printf("Enter group name (max 19 characters): ");
    fgets(name, 20, stdin);
    name[strlen(name) - 1] = '\0';
    sprintf(message, "/create %s", name);
    send(hSocket, message, strlen(message), 0);
    recv(hSocket, message, BUF_SIZE, 0);
    printf("%s\n", message);
}

void join_group(SOCKET hSocket) {
    char name[20], message[BUF_SIZE];
    printf("Enter group name (max 19 characters): ");
    fgets(name, 20, stdin);
    name[strlen(name) - 1] = '\0';
    sprintf(message, "/join %s", name);
    send(hSocket, message, strlen(message), 0);
    recv(hSocket, message, BUF_SIZE, 0);
    printf("%s\n", message);
}

void leave_group(SOCKET hSocket) {
    char message[BUF_SIZE];
    sprintf(message, "/leave");
    send(hSocket, message, strlen(message), 0);
    recv(hSocket, message, BUF_SIZE, 0);
    printf("%s\n