Windows 網絡編程實戰：TCP/UDP Socket 完整開發指南

編輯：關於C語言

核心區別

特性	TCP (SOCK_STREAM)	UDP (SOCK_DGRAM)
連接模式	面向連接，三次握手	無連接，數據報
可靠性	可靠、有序、無重複	不可靠、無序、可能重複/丟失
流控/擁塞控制	有	無
典型場景	檔案傳輸、Web、郵件、SSH	即時通訊、視訊串流、DNS、遊戲

Winsock 初始化（雙方通用）

WORD wVersion = MAKEWORD(2, 2); // 建議 2.2
WSADATA wsaData;
if (WSAStartup(wVersion, &wsaData) != 0) return;
if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
    WSACleanup(); return;
}
// 記得連結 ws2_32.lib
#pragma comment(lib, "ws2_32.lib")

TCP 服務端完整流程

// 1. 建立 socket
SOCKET sockSrv = socket(AF_INET, SOCK_STREAM, 0);

// 2. 綁定地址/端口
SOCKADDR_IN addrSrv = {};
addrSrv.sin_family = AF_INET;
addrSrv.sin_port = htons(6000);
addrSrv.sin_addr.S_un.S_addr = htonl(INADDR_ANY); // 監聽所有網卡
bind(sockSrv, (SOCKADDR*)&addrSrv, sizeof(addrSrv));

// 3. 監聽
listen(sockSrv, 5); // 佇列長度 5

// 4. 迴圈接受客戶端
SOCKADDR_IN addrClient;
int len = sizeof(addrClient);
while (true) {
    SOCKET sockCon = accept(sockSrv, (SOCKADDR*)&addrClient, &len);
    
    // 5. 收發數據
    char sendBuf[100];
    sprintf(sendBuf, "Welcome %s", inet_ntoa(addrClient.sin_addr));
    send(sockCon, sendBuf, strlen(sendBuf)+1, 0);
    
    char recvBuf[100];
    recv(sockCon, recvBuf, sizeof(recvBuf), 0);
    printf("Client: %s\n", recvBuf);
    
    closesocket(sockCon); // 關閉本次連接 socket
}
// 7. 關閉監聽 socket（通常不執行到這）
closesocket(sockSrv);
WSACleanup();

TCP 客戶端完整流程

SOCKET sockClient = socket(AF_INET, SOCK_STREAM, 0);

SOCKADDR_IN addrSrv = {};
addrSrv.sin_family = AF_INET;
addrSrv.sin_port = htons(6000);
addrSrv.sin_addr.S_un.S_addr = inet_addr("127.0.0.1"); // 服務端 IP

connect(sockClient, (SOCKADDR*)&addrSrv, sizeof(addrSrv));

// 雙向通訊
char recvBuf[100];
recv(sockClient, recvBuf, sizeof(recvBuf), 0);
printf("Server: %s\n", recvBuf);

send(sockClient, "Hello from Client", strlen("Hello from Client")+1, 0);

closesocket(sockClient);
WSACleanup();

UDP 服務端（無連接，單向/雙向均用 sendto/recvfrom）

SOCKET sockSrv = socket(AF_INET, SOCK_DGRAM, 0);

SOCKADDR_IN addrSrv = {};
addrSrv.sin_family = AF_INET;
addrSrv.sin_port = htons(6000);
addrSrv.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
bind(sockSrv, (SOCKADDR*)&addrSrv, sizeof(addrSrv));

SOCKADDR_IN addrClient;
int len = sizeof(addrClient);
char recvBuf[100];
recvfrom(sockSrv, recvBuf, sizeof(recvBuf), 0, (SOCKADDR*)&addrClient, &len);
printf("Received: %s\n", recvBuf);

char sendBuf[100];
sprintf(sendBuf, "UDP Server replies to %s", inet_ntoa(addrClient.sin_addr));
sendto(sockSrv, sendBuf, strlen(sendBuf)+1, 0, (SOCKADDR*)&addrClient, len);

closesocket(sockSrv);
WSACleanup();

UDP 客戶端

SOCKET sockClient = socket(AF_INET, SOCK_DGRAM, 0);

SOCKADDR_IN addrSrv = {};
addrSrv.sin_family = AF_INET;
addrSrv.sin_port = htons(6000);
addrSrv.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

sendto(sockClient, "Hello UDP Server", strlen("Hello UDP Server")+1, 0,
       (SOCKADDR*)&addrSrv, sizeof(addrSrv));

char recvBuf[100];
int len = sizeof(addrSrv);
recvfrom(sockClient, recvBuf, sizeof(recvBuf), 0, (SOCKADDR*)&addrSrv, &len);
printf("Server: %s\n", recvBuf);

closesocket(sockClient);
WSACleanup();