TCP与UDP协议的Socket编程详解(附详细示例)

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};
    const char *response = "Hello from TCP server";

    // 1. 创建TCP套接字（SOCK_STREAM表示流式套接字）
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 设置套接字选项，允许端口复用
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }
    
    // 配置地址信息（IPv4、任意本地IP、端口8080）
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    // 2. 绑定套接字到指定端口
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 3. 监听连接请求（最大等待队列长度为5）
    if (listen(server_fd, 5) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }
    
    printf("TCP Server listening on port %d...\n", PORT);

    // 4. 接受客户端连接（阻塞等待）
    if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
        perror("accept");
        exit(EXIT_FAILURE);
    }

    // 5. 读取客户端数据
    ssize_t valread = read(new_socket, buffer, BUFFER_SIZE);
    printf("Received from client: %s\n", buffer);

    // 向客户端发送响应
    send(new_socket, response, strlen(response), 0);
    printf("Response sent to client\n");

    // 6. 关闭连接
    close(new_socket);
    close(server_fd);
    return 0;
}

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int sock = 0;
    struct sockaddr_in serv_addr;
    char buffer[BUFFER_SIZE] = {0};
    const char *message = "Hello from TCP client";

    // 1. 创建TCP套接字
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\nSocket creation error\n");
        return -1;
    }

    // 配置服务器地址信息
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // 转换IP地址（字符串转二进制）
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported\n");
        return -1;
    }

    // 2. 连接服务器（三次握手在此过程完成）
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection failed\n");
        return -1;
    }

    // 3. 向服务器发送数据
    send(sock, message, strlen(message), 0);
    printf("Message sent to server\n");

    // 接收服务器响应
    ssize_t valread = read(sock, buffer, BUFFER_SIZE);
    printf("Received from server: %s\n", buffer);

    // 4. 关闭连接
    close(sock);
    return 0;
}

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int sockfd;
    char buffer[BUFFER_SIZE];
    struct sockaddr_in servaddr, cliaddr;
    const char *response = "Hello from UDP server";

    // 1. 创建UDP套接字（SOCK_DGRAM表示数据报套接字）
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    memset(&servaddr, 0, sizeof(servaddr));
    memset(&cliaddr, 0, sizeof(cliaddr));

    // 配置服务器地址信息
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = INADDR_ANY;
    servaddr.sin_port = htons(PORT);

    // 2. 绑定套接字到指定端口
    if (bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

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

    socklen_t len = sizeof(cliaddr);

    // 3. 接收客户端数据报（阻塞等待，同时获取客户端地址）
    ssize_t n = recvfrom(sockfd, (char *)buffer, BUFFER_SIZE, MSG_WAITALL, 
                        (struct sockaddr *)&cliaddr, &len);
    buffer[n] = '\0';
    printf("Received from client: %s\n", buffer);

    // 向客户端发送响应（需指定客户端地址）
    sendto(sockfd, (const char *)response, strlen(response), 
           MSG_CONFIRM, (const struct sockaddr *)&cliaddr, len);
    printf("Response sent to client\n");

    // 4. 关闭套接字
    close(sockfd);
    return 0;
}

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int sockfd;
    char buffer[BUFFER_SIZE];
    struct sockaddr_in servaddr;
    const char *message = "Hello from UDP client";

    // 1. 创建UDP套接字
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    memset(&servaddr, 0, sizeof(servaddr));

    // 配置服务器地址信息
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    socklen_t len = sizeof(servaddr);

    // 2. 向服务器发送数据报（需指定服务器地址）
    sendto(sockfd, (const char *)message, strlen(message), 
           MSG_CONFIRM, (const struct sockaddr *)&servaddr, sizeof(servaddr));
    printf("Message sent to server\n");

    // 接收服务器响应
    ssize_t n = recvfrom(sockfd, (char *)buffer, BUFFER_SIZE, 
                        MSG_WAITALL, (struct sockaddr *)&servaddr, &len);
    buffer[n] = '\0';
    printf("Received from server: %s\n", buffer);

    // 3. 关闭套接字
    close(sockfd);
    return 0;
}