tcp服务器c代码,客户端连接断开之后还可以重新连接服务器

以下是一个简单的TCP服务器的C代码示例，其中包含重新连接客户端的功能。当客户端连接断开时，服务器会等待一段时间然后尝试重新连接客户端，直到达到最大重试次数。在这个示例中，我们使用了一个简单的字符串协议，服务器将接收到的任何字符串转换为大写并将其发送回客户端。

#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>

#define MAX_RETRIES 10
#define RETRY_INTERVAL 5

void handle_client(int client_sock, struct sockaddr_in client_addr);
void handle_error(const char* message);

int main(int argc, char* argv[]) {
    int server_sock, client_sock, port;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s port\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    port = atoi(argv[1]);

    // create socket
    if ((server_sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        handle_error("socket");
    }

    // bind to port
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(port);

    if (bind(server_sock, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        handle_error("bind");
    }

    // listen for connections
    if (listen(server_sock, 5) == -1) {
        handle_error("listen");
    }

    printf("Server listening on port %d...\n", port);

    // accept connections
    while (1) {
        client_addr_len = sizeof(client_addr);
        if ((client_sock = accept(server_sock, (struct sockaddr*)&client_addr, &client_addr_len)) == -1) {
            handle_error("accept");
        }

        printf("Client connected: %s\n", inet_ntoa(client_addr.sin_addr));

        // handle client in a separate thread
        if (fork() == 0) {
            close(server_sock);
            handle_client(client_sock, client_addr);
            exit(EXIT_SUCCESS);
        }

        close(client_sock);
    }

    return 0;
}

void handle_client(int client_sock, struct sockaddr_in client_addr) {
    char buffer[1024];
    int retries = 0;

    while (1) {
        // receive message from client
        int bytes_received = recv(client_sock, buffer, sizeof(buffer), 0);
        if (bytes_received == 0) {
            printf("Client disconnected: %s\n", inet_ntoa(client_addr.sin_addr));
            break;
        } else if (bytes_received == -1) {
            handle_error("recv");
        }

        // convert message to uppercase
        for (int i = 0; i < bytes_received; i++) {
            buffer[i] = toupper(buffer[i]);
        }

        // send message back to client
        if (send(client_sock, buffer, bytes_received, 0) == -1) {
            handle_error("send");
        }
    }

    // try to reconnect client
    close(client_sock);
    printf("Retrying connection to client: %s\n", inet_ntoa(client_addr.sin_addr));
    while (retries < MAX_RETRIES) {
        sleep(RETRY_INTERVAL);
        if ((client_sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
            handle_error("socket");
        }

        if (connect(client_sock, (struct sockaddr*)&client_addr, sizeof(client_addr)) == 0) {
            printf("Client reconnected: %s\n", inet_ntoa(client_addr.sin_addr));
            handle_client(client_sock, client_addr);
            return;
        }

        retries++;
        printf("Connection attempt #%d failed\n", retries);
    }

    printf("Maximum retries reached, giving up on client: %s\n", inet_ntoa(client_addr.sin_addr));
}

void handle_error(const char* message) {
    perror(message);
    exit(EXIT_FAILURE);
}