筆記-TCP/IP socket編程

TCP 編程

涉及函數

函數定義在 sys/socket.h，相關數據類型定義在 sys/types.h。

客戶端									服務端
socket									socket
										bind
										listen
										accept
connect
send/recv								send/recv
close									close

程序流圖

UDP 編程

涉及函數

函數定義在 sys/socket.h，相關數據類型定義在 sys/types.h。

客戶端									服務端
socket									socket
										bind
sendto/recvfrom							recvfrom/sendto
close									close

程序流圖

編程實例

TCP 服務端

#include <unistd.h>
#include <arpa/inet.h>
#define MAXBUF 1024  

// 簡單判斷一下是否是IPv6地址
inline bool isipv6(const char* ip)
{   
    return ip? strchr(ip, ':') : false;
}

int main(int argc, char **argv)
{
    int sockfd, new_fd;
    socklen_t len;

    int family = AF_INET;
    union {
        struct sockaddr     sa;
        struct sockaddr_in  sa4;  // IPv4
        struct sockaddr_in6 sa6;  // IPv6
    } myaddr, theiraddr;


    unsigned int myport, lisnum;
    char buf[MAXBUF + 1];

    if (argv[1])
        myport = atoi(argv[1]);
    else
        myport = 8088;

    if (argv[2])
        lisnum = atoi(argv[2]);
    else
        lisnum = 2;

    if (isipv6(argv[3])) {
        family = AF_INET6;
    }

   if ((sockfd = socket(family, SOCK_STREAM, 0)) == -1) {  
        perror("socket");
        exit(1);
    } else
        printf("socket created\n");

    bzero(&myaddr, sizeof(myaddr));
    if (family == AF_INET) { // IPv4
        myaddr.sa4.sin_family = AF_INET;
        myaddr.sa4.sin_port = htons(myport);
        if (argv[3])
            inet_pton(AF_INET, argv[3], &myaddr.sa4.sin_addr);
        else
            myaddr.sa4.sin_addr.s_addr = INADDR_ANY;
    } else { // IPv6
        myaddr.sa6.sin6_family = AF_INET6;
        myaddr.sa6.sin6_port = htons(myport);
        if (argv[3])
            inet_pton(AF_INET6, argv[3], &myaddr.sa6.sin6_addr);
        else
            myaddr.sa6.sin6_addr = in6addr_any;
    }

    if (bind(sockfd, (struct sockaddr *) &myaddr, sizeof(myaddr)) == -1) {
    } else
        printf("binded\n");

    if (listen(sockfd, lisnum) == -1) {
        perror("listen");
        exit(1);
    } else
        printf("begin listen\n");

    while (1) {
        len = sizeof(theiraddr);
        if ((new_fd = accept(sockfd, (struct sockaddr *) &theiraddr,  &len)) == -1) {
            perror("accept");
            exit(errno);
        } else {
            if (theiraddr.sa.sa_family == AF_INET)
                printf("server: got connection from %s, port %d, socket %d\n",
                    inet_ntop(AF_INET, &theiraddr.sa4.sin_addr, buf, sizeof(buf)),
                    ntohs(theiraddr.sa4.sin_port), new_fd);

            else
                printf("server: got connection from %s, port %d, socket %d\n",
                    inet_ntop(AF_INET6, &theiraddr.sa6.sin6_addr, buf, sizeof(buf)),
                    ntohs(theiraddr.sa6.sin6_port), new_fd);
        }
        /* 開始處理每個新連接上的數據收發 */
        bzero(buf, MAXBUF + 1);
        strcpy(buf,
               "這是在連接建立成功後向客戶端發送的第一個消息\n只能向new_fd這個用accept函數新建立的socket發消息，不>能向sockfd這個監聽socket發送消息，監聽socket不能用來接收或發送消息");
        /* 發消息給客戶端 */
        len = send(new_fd, buf, strlen(buf), 0);
        if (len < 0) {
            printf
                ("消息'%s'發送失敗！錯誤代碼是%d，錯誤信息是'%s'\n",
                 buf, errno, strerror(errno));
        } else
            printf("消息'%s'發送成功，共發送了%d個字節！\n",
                   buf, len);

        bzero(buf, MAXBUF + 1);
        /* 接收客戶端的消息 */
        len = recv(new_fd, buf, MAXBUF, 0);
        if (len > 0)
            printf("接收消息成功:'%s'，共%d個字節的數據\n",
                   buf, len);
        else
            printf
                ("消息接收失敗！錯誤代碼是%d，錯誤信息是'%s'\n",
                 errno, strerror(errno));
        /* 處理每個新連接上的數據收發結束 */
    }

    close(sockfd);
    return 0;
}

TCP 客戶端

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <resolv.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAXBUF 1024  

inline bool isipv6(const char* ip)
{
    return ip? strchr(ip, ':') : false;
}

int main(int argc, char **argv)
{
    int sockfd, len;
    int family = AF_INET;
    union {
        struct sockaddr     sa;
        struct sockaddr_in  sa4; // IPv4  
        struct sockaddr_in6 sa6; // IPv6
    } dest;

    char buffer[MAXBUF + 1];

    if (argc != 3) {
        printf("參數格式錯誤！正確用法如下：\n\t\t%s IP地址 端口\n\t比如:\t%s 127.0.0.1 80\n此程序用來從某個 IP 地址的服務器某個端口接收最多 MAXBUF 個字節的消息\n",
             argv[0], argv[0]);
        exit(0);
    }

    if (isipv6(argv[1])) {
        family = AF_INET6;
    }

    /* 創建一個 socket 用於 tcp 通信 */
    if ((sockfd = socket(family, SOCK_STREAM, 0)) < 0) {
        perror("Socket");
        exit(errno);
    }
    printf("socket created\n");

    /* 初始化服務器端（對方）的地址和端口信息 */
    bzero(&dest, sizeof(dest));
    if (family == AF_INET) { // IPv4
        dest.sa4.sin_family = AF_INET;
        dest.sa4.sin_port = htons(atoi(argv[2]));
        inet_pton(AF_INET, argv[1], &dest.sa4.sin_addr);
    } else { // IPv6
        dest.sa6.sin6_family = AF_INET6;
        dest.sa6.sin6_port = htons(atoi(argv[2]));
        inet_pton(AF_INET6, argv[1], &dest.sa6.sin6_addr);
    }
    printf("address created\n");

    /* 連接服務器 */
    if (connect(sockfd, (struct sockaddr *) &dest, sizeof(dest)) != 0) {
        perror("Connect ");
        exit(errno);
    }
    printf("server connected\n");

    /* 接收對方發過來的消息，最多接收 MAXBUF 個字節 */
    bzero(buffer, MAXBUF + 1);
    /* 接收服務器來的消息 */
    len = recv(sockfd, buffer, MAXBUF, 0);
    if (len > 0)
        printf("接收消息成功:'%s'，共%d個字節的數據\n",
               buffer, len);
    else
        printf
            ("消息接收失敗！錯誤代碼是%d，錯誤信息是'%s'\n",
             errno, strerror(errno));

    bzero(buffer, MAXBUF + 1);
    strcpy(buffer, "這是客戶端發給服務器端的消息");
    /* 發消息給服務器 */
    len = send(sockfd, buffer, strlen(buffer), 0);
    if (len < 0)
        printf
            ("消息'%s'發送失敗！錯誤代碼是%d，錯誤信息是'%s'\n",
             buffer, errno, strerror(errno));
    else
        printf("消息'%s'發送成功，共發送了%d個字節！\n",
               buffer, len);

    /* 關閉連接 */
    close(sockfd);
    return 0;
}

UDP 服務端

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <string.h>
#define LOCALPORT 8088  
#define MAXBUF    1024

inline bool isipv6(const char* ip)
{   
    return ip? strchr(ip, ':') : false;
}

int main(int argc,char *argv[])
{
    int mysocket, len;
    int i=0;
    int family = AF_INET;
    union {
        struct sockaddr     sa;
        struct sockaddr_in  sa4;
        struct sockaddr_in6 sa6;
    }  addr, theiraddr;
    int addr_len;
    char msg[MAXBUF];
    char buf[INET6_ADDRSTRLEN];
    char* myip = NULL;
    int myport = LOCALPORT;

    if (argc > 1)
        myport = atoi(argv[1]);
    if (argc > 2)
        myip = argv[2];

    if (isipv6(myip))
        family = AF_INET6;

    if((mysocket = socket(family, SOCK_DGRAM, 0)) < 0) {
        perror("error");
        return(1);
    } else {
        printf("socket created ...\n");
        printf("socket id: %d \n",mysocket);
    }

    bzero(&addr, sizeof(addr));
    if (family == AF_INET) { // IPv4
        addr.sa4.sin_family = AF_INET;
        addr.sa4.sin_port = htons(myport);
        if (myip)
            inet_pton(AF_INET, myip, &addr.sa4.sin_addr);
        else
            addr.sa4.sin_addr.s_addr = INADDR_ANY;
    } else { // IPv6
        addr.sa6.sin6_family = AF_INET6;
        addr.sa6.sin6_port = htons(myport);
        if (myip)
            inet_pton(AF_INET6, myip, &addr.sa6.sin6_addr);
        else
            addr.sa6.sin6_addr = in6addr_any;
    }

    if(bind(mysocket, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("connect");
        exit(1);
    } else {
        printf("bink ok.\n");
        printf("local port: %d\n", myport);
    }

    while(1) {
        addr_len = sizeof(theiraddr);
        bzero(&addr, sizeof(theiraddr));
        bzero(msg, sizeof(msg));
        len = recvfrom(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&theiraddr, (socklen_t*)&addr_len);
        printf("%d:", i);
        i++;
        if (theiraddr.sa.sa_family == AF_INET) { // IPv4
            inet_ntop(AF_INET,&theiraddr.sa4.sin_addr,buf,sizeof(buf));
        } else { // IPv6
            inet_ntop(AF_INET6,&theiraddr.sa6.sin6_addr,buf,sizeof(buf));
        }
        printf("message from ip %s, ", buf);
        printf("Received message: %s\n", msg);
        if(sendto(mysocket, msg, len, 0, (struct sockaddr *)&theiraddr, addr_len)<0) {
            printf("error");
            exit(1);
        }
    }
    /* 關閉連接 */
    close(mysocket);
    return 0;
}

UDP 客戶端

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/socket.h>
#include <string.h>
#define REMOTEPORT 8088  
#define REMOTEIP "127.0.0.1"  
#define MAXBUF    1024

inline bool isipv6(const char* ip)
{   
    return ip? strchr(ip, ':') : false;
}

int main(int argc,char *argv[])
{
    int mysocket,len;
    int i=0;
    int family = AF_INET;
    union {
        struct sockaddr     sa;
        struct sockaddr_in  sa4;
        struct sockaddr_in6 sa6;
    }  addr;
    int addr_len;
    char msg[MAXBUF];
    char* remoteip = (char*)REMOTEIP;
    int remoteport = REMOTEPORT;

    if (argc > 1)
        remoteport = atoi(argv[1]);
    if (argc > 2)
        remoteip = argv[2];

    if (isipv6(remoteip))
        family = AF_INET6;

    if((mysocket = socket(family, SOCK_DGRAM, 0)) < 0) {
        perror("error");
        exit(1);
    } else {
        printf("socket created ...\n");
        printf("socket id: %d \n", mysocket);
        printf("rmote ip: %s \n", remoteip);
        printf("remote port: %d \n", remoteport);
    }

    addr_len = sizeof(addr);
    bzero(&addr, sizeof(addr));
    if (family == AF_INET) { // IPv4
        addr.sa4.sin_family = AF_INET;
        addr.sa4.sin_port = htons(remoteport);
        inet_pton(AF_INET, remoteip, &addr.sa4.sin_addr);
    } else { // IPv6
        addr.sa6.sin6_family = AF_INET6;
        addr.sa6.sin6_port = htons(remoteport);
        inet_pton(AF_INET6, remoteip, &addr.sa6.sin6_addr);
    }

    while(1) {
        bzero(msg, sizeof(msg));
        len = read(STDIN_FILENO, msg, sizeof(msg));
        if(sendto(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&addr, addr_len) < 0) {
            perror("error");
            exit(1);
        }
        bzero(msg, sizeof(msg));
        len = recvfrom(mysocket, msg, sizeof(msg), 0, (struct sockaddr *)&addr, (socklen_t*)&addr_len);
        printf("%d: ", i);
        i++;
        printf("Received message: %s\n", msg);
    }
    /* 關閉連接 */
    close(mysocket);
    return 0;
}

參考

[1] https://www.cnblogs.com/wuyuxuan/p/5541598.html
[2] https://blog.csdn.net/qq_26437925/article/details/51892362