C++ Socket庫實現連接超時重試

在C++中，我們可以使用<sys/socket.h>和<netinet/in.h>庫來實現一個帶有超時重試功能的Socket客戶端。以下是一個簡單的示例，展示了如何實現連接超時重試功能：

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <chrono>
#include <thread>

const int MAX_RETRIES = 5;
const int RETRY_DELAY = 2; // seconds
const std::string SERVER_IP = "127.0.0.1";
const int SERVER_PORT = 8080;

bool connect_with_retry(int retries) {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        std::cerr << "Error creating socket" << std::endl;
        return false;
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    inet_pton(AF_INET, SERVER_IP.c_str(), &server_addr.sin_addr);

    for (int i = 0; i < retries; ++i) {
        if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == 0) {
            std::cout << "Connected to server successfully" << std::endl;
            return true;
        } else {
            std::cerr << "Connection failed, retrying in " << RETRY_DELAY << " seconds..." << std::endl;
            std::this_thread::sleep_for(std::chrono::seconds(RETRY_DELAY));
        }
    }

    std::cerr << "Failed to connect to server after " << retries << " retries" << std::endl;
    close(sockfd);
    return false;
}

int main() {
    if (connect_with_retry(MAX_RETRIES)) {
        // Perform the rest of your communication here
        close(sockfd);
    } else {
        std::cerr << "Failed to connect to server" << std::endl;
    }

    return 0;
}

在這個示例中，我們定義了一個connect_with_retry函數，它嘗試連接到指定的服務器和端口。如果連接失敗，它將等待一段時間然后重試，直到達到最大重試次數。如果所有嘗試都失敗了，函數將返回false。

請注意，這個示例僅用于演示目的，實際應用中可能需要根據具體需求進行調整。例如，你可能需要設置不同的超時時間、重試次數限制以及錯誤處理策略。