picotcp/lwip ipv4/ipv6 fully functional, needs stress testing

tests/api_test/tcpclient4.c

@@ -0,0 +1,49 @@
+// TCP Client test program
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+ 
+int atoi(const char *str);
+int close(int filedes);
+
+int main(int argc , char *argv[])
+{
+    if(argc < 3) {
+        printf("usage: client <addr> <port>\n");
+        return 1;
+    }
+   
+    int sock, port = atoi(argv[2]);
+    struct sockaddr_in server;
+    char message[1000] , server_reply[2000];
+     
+    sock = socket(AF_INET , SOCK_STREAM , 0);
+    if (sock == -1) {
+        printf("could not create socket");
+    }     
+    server.sin_addr.s_addr = inet_addr(argv[1]);
+    server.sin_family = AF_INET;
+    server.sin_port = htons( port );
+ 
+    printf("connecting...\n");
+    if (connect(sock , (struct sockaddr *)&server , sizeof(server)) < 0) {
+        perror("connect failed. Error");
+        return 1;
+    }
+    printf("connected\n");
+
+    char *msg = "welcome to the machine!";
+    // TX         
+    if(send(sock, msg, strlen(msg), 0) < 0) {
+        printf("send failed");
+        return 1;
+    }
+    else {
+        printf("sent message: %s\n", msg);
+        printf("len = %ld\n", strlen(msg));
+    }
+    close(sock);
+    return 0;
+}