在c++中setsockopt怎樣設置重傳選項

在C++中，setsockopt函數用于設置套接字選項

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

int main() {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        std::cerr << "Error creating socket" << std::endl;
        return 1;
    }

    // 設置重傳選項
    int retransmit_interval = 5; // 重傳間隔時間（秒）
    int retransmit_count = 3; // 重傳次數

    struct timeval tv;
    tv.tv_sec = retransmit_interval;
    tv.tv_usec = 0;

    if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv)) == -1) {
        std::cerr << "Error setting send timeout" << std::endl;
        close(sockfd);
        return 1;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv)) == -1) {
        std::cerr << "Error setting receive timeout" << std::endl;
        close(sockfd);
        return 1;
    }

    // 設置重傳次數選項（僅適用于TCP）
    int tcp_retransmit_count = retransmit_count;
    if (setsockopt(sockfd, IPPROTO_TCP, TCP_RETRANSMIT_COUNT, (char*)&tcp_retransmit_count, sizeof(tcp_retransmit_count)) == -1) {
        std::cerr << "Error setting TCP retransmit count" << std::endl;
        close(sockfd);
        return 1;
    }

    // 連接到服務器
    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    inet_pton(AF_INET, "127.0.0.1", &(server_addr.sin_addr));

    if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        std::cerr << "Error connecting to server" << std::endl;
        close(sockfd);
        return 1;
    }

    // 向服務器發送數據
    std::string message = "Hello, server!";
    if (send(sockfd, message.c_str(), message.size(), 0) == -1) {
        std::cerr << "Error sending data" << std::endl;
        close(sockfd);
        return 1;
    }

    // 從服務器接收數據
    char buffer[1024];
    ssize_t received = recv(sockfd, buffer, sizeof(buffer) - 1, 0);
    if (received == -1) {
        std::cerr << "Error receiving data" << std::endl;
    } else {
        buffer[received] = '\0';
        std::cout << "Received from server: " << buffer << std::endl;
    }

    close(sockfd);
    return 0;
}

請注意，這個示例僅適用于TCP套接字。對于UDP套接字，您需要使用setsockopt函數設置SO_BROADCAST和SO_REUSEADDR選項。此外，重傳次數選項（TCP_RETRANSMIT_COUNT）僅適用于TCP協議。